The 'Battle of St Malo' was fought between Allied and German forces for control of the north-western French coastal town of St Malo (4 August/2 September 1944).
The battle was part of the Allied break-out across France from the Normandy lodgement created in 'Overlord' after the 'Neptune' (iii) amphibious assault on 6 June. US Army units, with the support of Free French and British forces, laid siege to the town and defeated its German defenders, though the latter’s garrison on a nearby island continued to resist until 2 September.
St Malo was one of the French towns designated as a Festung (fortress) under the German 'Atlantikwall' programme, and its prewar defences were expanded considerably before the Allied landings in Normandy. As part of their invasion plans, the Allies intended to capture the town so that its port could be used to land supplies. While there was some debate over the necessity of this during August as the Allied forces broke out of Normandy and entered Brittany, it was decided to capture rather than merely contain St Malo to secure its port and eliminate the German garrison. After initial attempts to capture the locality failed, the US Army began a siege operation. Infantry units attacked and defeated large numbers of fortified German positions with the support of artillery and aircraft. A fortification on the edge of St Malo was the final German position on the mainland to hold out, and surrendered on 17 August. After extensive air and naval bombardments, the garrison on the nearby island of Cézembre surrendered on 2 September. It was then discovered that German demolitions had made impractical the notion of using St Malo as a resupply port.
St Malo is a historic port town on Brittany’s northern coast and was, as a result of its strategic location, extensively fortified over the centuries. In 1936, when it was a popular holiday destination for wealthy Parisians and boasted a casino, hotels and spas, St Malo had a population of 13,000 persons, of whom 6,000 lived within the city walls. St Malo’s harbour facilities could accommodate medium-sized ships and unload 1,000 tons of cargo per day. The town is located on the north-west of the eponymous peninsula, on the eastern side of the mouth of the Rance river. St Malo was once an island, but had been joined to the mainland by a causeway and a road by the time of World War II. The suburb of Paramé was to the east of St Malo, and the fishing port of St Servan sur Mer to the south. Dinard lies across the Rance river from St Malo, and the small but heavily fortified island of Cézembre is located in the mouth of the Rance river some 4,000 yards (3660 m) off the coast from St Malo.
During the first months of World War II, St Malo was one of the ports used to import supplies for the British Expeditionary Force in France. As the Germans neared victory in the 'Battle of France', Allied forces were also evacuated to the UK from the town during the 'Aerial' undertaking in June 1940: 21,474 personnel were embarked from St Malo without the loss of lives or ships. Brittany was a key centre for German forces during the occupation of France and its major ports were used as U-boat and, on occasion, capital ship bases. As the Allies prepared to liberate France, the Germans judged that Brittany was a likely location for an Allied invasion. This led to the construction of extensive fortifications in the region as part of the 'Atlantikwall' programme. In 1943 the Oberkommando der Wehrmacht designated St Malo and other French ports with pre-war fortifications as Festungen. Each fortress was assigned a commander who was required to swear an oath to defend his charge to the death. Adolf Hitler expected that these fortresses would hold out for at least 90 days if they were attacked.
St Malo lay within the occupied zone of France, which was directly administered by the German military rather than the Vichy French régime. During the occupation, the town’s port was used as a base for coastal forces by the Kriegsmarine, and was also a supply base for the large German garrison in the Channel Islands. The 'Atlantikwall' programme led to a substantial upgrading of St Malo’s pre-war fortifications, this work being undertaken by volunteer and forced labourers controlled by the Organization 'Todt'.
The French resistance movement had large numbers of members in Brittany and proved itself capable of delivering successful attacks on German forces. The region’s resistance movement was dominated by the communist Francs-Tireurs et Partisans who, unlike many other resistance units, favoured the launching of attacks before the Allies landed in France. This led to a partisan war that intensified from 1943. The German forces seeking to suppress the resistance included the Gestapo secret police, army military police formations and security battalions. Many of the latter were manned by captured Soviet personnel who agreed to fight for the Germans. The German units were under orders to kill any partisans taken prisoner, and at the same time the Free French did not accept their opponents' surrender. Allied air forces started to air-drop supplies to the Free French in Brittany from a time early in 1944, and special forces units were inserted from June that year to strengthen the resistance. There were more than 2,500 resistance members in the St Malo region as of August 1944, most of them living in the towns of St Malo, Dinard and Dinan.
As part of the preparations for the 'Overlord' campaign in Normandy, St Malo was identified by Allied planners as one of several minor ports on the French English Channel and Atlantic coasts that could be used for the landing of supplies for the Allied ground forces in France. It was intended that these ports would provide a useful supplement for the major ports such as Brest, Cherbourg and Quiberon Bay. At this time, the planners envisaged that the initial invasion phase would be followed by a subsequent phase to secure a significant lodgement, which was to include all of the French coast between the mouths of the Seine and Loire rivers and nearby inland areas, including Normandy and Brittany. It was believed that this region could be secured within three months of the invasion. Facilities constructed within the lodgement area and supplies and troops landed there would be used to support the subsequent liberation of France and invasion of Germany. The 'Overlord' plan therefore specified that securing Brittany would be the main objective of Lieutenant General Omar N. Bradley’s US 12th Army Group after it broke out from Normandy. This task was assigned to the US 3rd Army, which formed part of the army group and was commanded by Lieutenant General George S. Patton. The planners believed that it would be possible to open St Malo to Allied shipping 27 days after the 'Neptune' (iii) landings in Normandy if Allied advances following the invasion went as scheduled, and that 900 tons of supplies could initially be unloaded there daily via DUKW amphibious trucks. It was hoped that port capacity could subsequently be increased to 3,000 tons of supplies per day at St Malo, and another 6,000 tons per day at the ports in the region such as Cancale. This would allow the St Malo area to be the main port for the sustenance of the US 3rd Army. However, St Malo’s port was also assessed as being easily blocked by German forces.
After the 'Neptune' (iii) landings on 6 June 1944, the Allies and Germans fought a prolonged campaign in the region. The German forces managed to prevent the Allies from breaking out of the peninsula into other parts of France for almost two months but in the process suffered heavy casualties. Early in July the Allied leadership considered the feasibility of launching combined amphibious and airborne landings at St Malo, Quiberon Bay and Brest to seize ports, but it was decided that such undertakings would be very risky, leading to a decision to attempt them only in the event that the stalemate in Normandy became prolonged. British bombers attacked railway yards and fuel storage tanks at St Malo on 17 July, and this raid also caused French civilian casualties. Late in July the US forces in the west of the Normandy region launched the 'Cobra' break-out offensive, which led the German positions to collapse. Avranches, through which the main roads leading from the west coast of Normandy into Brittany ran, was liberated on 30 July and a German counterattack was defeated on the following day. Large numbers of highly mobile US formations and units passed through the town over the next days, and rapidly penetrated ever deeper into the interior of France.
Patton’s initial plans for the liberation of Brittany involved first cutting off the Germans in the peninsula by driving a force from Avranches to Quiberon Bay. His armoured units would then rapidly capture the plateau in the centre of the Brittany peninsula, which would isolate the German garrison in a few port towns, and these towns were to be attacked as the final stage of the operation. Lieutenant General Omar N. Bradley, commander of the US 12th Army Group, initially ordered Patton to capture St Malo as part of securing Brittany. Patton did not consider the town’s capture to be important in its own right, and therefore assigned none of his forces to this task. Bradley did not object, and Patton gained his agreement to bypass the St Malo area if it proved to be well defended. At this time, the Allied intelligence services believed that there were 3,000 Germans at St Malo, and Patton thought that the entirety of the Breton peninsula was held by about 10,000 German troops: these estimates were much lower than the actual size of the garrisons. The collapse of the German army in France as the Allies broke out of Normandy early in August led the Allied leadership to change its thinking about Brittany. By 2 August General Dwight D. Eisenhower, the Supreme Commander of the Allied Expeditionary Force, believed that the main effort should be encircling the German forces to the south-east of Normandy rather than securing the peninsula. Bradley’s views also changed, and by 3 August he preferred that Patton assign only minimum strength to Brittany, and concentrate his main strength for an advance to the east. Thus the US VIII Corps, under Major General Troy H. Middleton, was given responsibility for the Brittany operations.
Major General Robert W. Grow’s US 6th Armored Division led the advance into western Brittany with the object of the rapid seizure of Brest, while Major General John S. Wood’s US 4th Armored Division pushed southward to liberate Rennes and then Quiberon Bay. On 2 August all the German Army units in Brittany were ordered to withdraw into the fortified ports, including St Malo, by the headquarters of their parent formation, General Wilhelm Fahrmbacher’s XXV Corps. St Malo was attacked by Allied aircraft again on 1 August. The US Navy also patrolled the Gulf of St Malo, and US destroyers and PT-boats engaged German coastal craft in the area on several occasions during the early days of August. On 3 August, the resistance forces in Brittany were directed to launch widespread attacks on the German occupation forces but at the same time to avoid major battles. There were approximately 35,000 armed resistance fighters in Brittany at the time, and these swiftly seized most of the region outside the towns including strategically important roads and bridges. The resistance’s control of these areas and transport infrastructure facilitated the VIII Corps' rapid advance, and resistance fighters also guided US forces as they moved through Brittany and undertook some garrison duties.
Before the 'Neptune' (iii) Allied landings in Normandy, Oberst Rudolf Bacherer’s 77th Division was stationed in the St Malo area. This formation had been created on 15 February 1944 near Caen in Normandy, and had been transferred to St Malo during May. The division was despatched to Normandy soon after D-Day, and suffered heavy casualties in the fighting there. The remnants of the division returned to St Malo late in July, where it was reinforced with two anti-partisan units, the 602nd Ostbataillon and the 1220th Sicherungsbataillon. It was later sent forward again as part of the extemporised which unsuccessfully attempted to check the US break-out at Avranches.
At the time of the battle, the German strength in the St Malo area was about 12,000 men. The garrison included the remnants of the 77th Division, and other army units included the 266th Division's 3/897th Grenadierregiment, the 602nd Ostbataillon, the 636th Ostbataillon and 1220th Sicherungsbataillon. Luftwaffe units in the area comprised the 15th Flakregiment and several other air-defence units, and the Kriegsmarine’s contribution included two coastal artillery units, the 260th Marineartillerieabteilung and the 1271st Heeresküstenbataillon.
The St Malo area was extensively fortified. The old town was enclosed by walls with thick stone ramparts on their seaward side. Its landward entrance was protected by a fortified château that had once been the home of Anne of Brittany, the duchess of Brittany between 1488 and 1514. The Fort de la Cité d’Aleth, which was designated as the Zitadelle (citadel) by the Germans, was located on a rocky promontory between St Malo and St Servan sur Mer: this had originally been designed by the great engineer Sébastien Le Prestre de Vauban in the 18th century. Several other fortresses were located on the approaches to St Malo, including the Fort la Varde at the Pointe de la Varde on the coast, the St Ideuc strongpoint to the east of Paramé, and fortifications on St Joseph’s Hill to the south-east of the town. Artillery in the fortifications on Cézembre provided support. Barbed wire and other obstacles had been sited on the beaches in the area to deter amphibious landings. The Germans had also planned to dig an anti-tank ditch across the St Malo peninsula and fill it with water, but this was incomplete. The fortifications in the St Malo area were positioned in such a way that their garrisons were able to support one another. They were also stocked with ammunition, water and food. Further supplies could be brought in by sea from the Channel Islands. While the Oberbefehlshaber 'West' judged that the fortifications of St Malo were the most complete of any in his command area at the time of the battle, they were incomplete, and a major deficiency was the relative paucity of artillery.
The St Malo garrison was designated Küstenverteidigungsgruppe 'Rance' (Coastal Defence Group 'Rance'), and was divided into three subgroups. St Malo and nearby towns were defended by the Küstenverteidigunguntergruppe 'St Malo' (Coastal Defence Subgroup 'St Malo'), or KVU St Malo, comprising 79 fortified positions. The area round the town of Dol de Bretagne to the south-east of St Malo was the responsibility of the Küstenverteidigunguntergruppe 'Dol' and included seven fortified positions, and the Küstenverteidigunguntergruppe 'Cancale' was assigned the section of the peninsula to the north-east of St Malo and included 16 fortified positions. The sector on the western side of the Rance river, around Dinard, was the responsibility of the remnants of the 77th Division, which was assigned some StuG III assault guns of the 341st StuGbrigade. Several strongpoints had been constructed to bolster the area’s defences, and these included four fortified artillery positions.
Cézembre was garrisoned by the [e[1st Batterie of the 608th Marineartillerieregiment, armed with several French 194-mm (7.64-in) guns, anti-aircraft guns and other weapons. The personnel on the island included some 100 men contributed by the Italian Social Republic, and this garrison came under the command of the German forces in the Channel Islands.
The fortress commander was Oberst Andreas von Aulock, a notable veteran who was disappointed to command a fortress as he would have preferred command of mobile forces. The readiness of von Aulock and other German commanders in the St Malo region to obey their orders to continue the fighting until further resistance was impossible led to the prolonged battle for the region. During the battle, when he had his headquarters in the citadel, von Aulock stated that 'I was placed in command of this fortress. I did not request it. I will execute the orders I have received and, doing my duty as a soldier, I will fight to the last stone'.
The extemporised Task Force A was the first US unit to enter the St Malo area. This force was established by Patton late in July for the rapid seizure of the bridges on the railway line connecting Paris and Brest, which ran along the north coast of Brittany, before these bridges were demolished by German forces. Commanded by Brigadier General Herbert L. Earnest, Task Force A comprised the 15th Cavalry Group, the 159th Engineer Battalion and the headquarters of the 1st Tank Destroyer Brigade. The task force passed through Avranches on 3 August, and engaged German forces 2 miles (3.2 km) from Dol de Bretagne on the same day. The commander of the 15th Cavalry Group was killed in the initial clash, and Earnest decided to bypass Dol de Bretagne to the south after learning from civilians that it was heavily defended. Middleton ordered the task force to probe St Malo’s defences as it pushed to the west, and thus investigate how strongly the town was held. This led to fighting near Miniac, 7 miles (11 km) to the west of Dol de Bretagne. As the Americans advanced towards St Malo, they encountered stronger defences to the south of Châteauneuf d’Ille et Vilaine. As a result of the German defence’s strength, Earnest asked Middleton for he urgent despatch of infantry to support his command. The 330th Infantry of Major General Robert C. Macon’s 83rd Division was entering the area at the time, and reached Dol de Bretagne during the afternoon of 3 August. The regiment’s commander decided to delay his attack on the town until the next day in order to allow his men sufficient time to defeat the many German defensive positions.
The 330th Infantry attacked Dol de Bretagne on the morning of 4 August, and quickly captured the town. Task Force A also continued to advance to the north toward Châteauneuf d’Ille et Vilaine during the day. This led to heavy fighting during which German coastal artillery and naval vessels in the St Malo area fired on the US troops.
Despite Patton’s desire to avoid a siege, Middleton concluded that the German force at St Malo was too strong to be safely bypassed as its defenders could otherwise have sallied to attack the supply lines supporting the Allied advance into Brittany. Middleton therefore ordered the 83rd Division to capture the area. Patton partially overruled him, believing that the Germans would offer only a token defence of the town and that the 330th Infantry was therefore all that would be needed to take it. Patton preferred that the rest of the 83rd Division follow Grow’s 6th Armored Division to Brest. However, events during the afternoon of 4 August proved that Middleton was correct. While the Germans withdrew to the north in the morning, more heavy fighting during the afternoon indicated that they were strengthening their positions. Accordingly, Middleton again ordered the concentration of the entire 83rd Division in the St Malo area to deliver a quick attack on the town in conjunction with Task Force A in the hope that this would crack the German defences. The remainder of the division arrived at Dol de Bretagne on the afternoon of 4 August, and its three regiments were deployed on the eastern side of the Rance river. The 83rd Division had landed in Normandy on 19 June, and taken part in the fighting there during July. It had overcome strong German resistance during 'Cobra' and followed the 6th Armored Division into Brittany.
US attacks on 5 August demonstrated that St Malo would not fall quickly. The 331st Infantry advanced along the coast and penetrated the first line of German defences near St Benoît des Ondes. Châteauneuf d’Ille et Vilaine was also captured, Task Force A taking 655 prisoners. One battalion of the 329th Infantry crossed the Rance river in assault boats as the first stage of an operation intended to secure the rapid capture of Dinard, but met by strong German resistance this unit had to be withdrawn. As it was clear that further fighting would be prolonged, Middleton directed Task Force A to disengage from the St Malo area during the night of 5/6 August and resume its mission of securing railway bridges. One of the 330th Infantry’s three battalions was detached from 5 August to 25 September to reinforce Task Force A.
Early in August, Bradley reached the conclusion that St Malo should be captured, and ordered that this take place. He believed that it would provide a useful port to supply the large US force in Brittany. The Americans still underestimated the size of German forces in St Malo at this time. While French personnel had advised them that there were around 10,000 Germans in the area, US estimates ranged from 3,000 to 6,000, and as on 12 |August the VIII Corps believed the garrison totalled 5,000 men at a time when there were actually more than 12,000 Germans in the St Malo area. Nevertheless, the stubborn resistance demonstrated by the Germans during the early fighting around St Malo convinced Middleton and Macon that it would be difficult to capture the town.
von Aulock had prepared for a lengthy battle, and rejected a proposal from local civilians to surrender and thereby prevent damage to the towns in the region. On 3 August he informed community leaders that most civilians would be expelled from St Malo for their own safety. When the leaders asked him to declare the town an open city to avoid fighting, von Aulock stated that after he had raised the matter with his superiors, Hitler had ordered him to fight to the last man. He further claimed that as his forces included armed vessels that were operating near St Malo, it was not possible to declare the town an open city as these vessels were legitimate targets for the Allies. During the evening of 5 August most of St Malo’s population departed the town and entered areas controlled by the Americans. As part of an effort to consolidate their positions, in the evening of 5 August the German forces withdrew from Cancale as well as the town of Dinan on the western bank of the Rance river.
US troops attacked toward St Malo on 6 August when, despite artillery and aircraft support, the pace of the advance was slow. By the afternoon the division was in contact with the German main defences, which included barbed wire entanglements, minefields and pillboxes armed with machine guns. The advance brought the Americans within range of the guns on Cézembre, which opened fire. One of the first shells to be fired hit and knocked down the spire of St Malo’s cathedral. As a result of the slow progress, Middleton reinforced the 83rd Division on this day with the 121st Infantry of Major General Donald A. Stroh’s 8th Division, one company of medium tanks and one artillery b, and also requested more air support. The 121st Infantry was allocated the task of capturing Dinard. The number of US troops assigned to the St Malo area eventually reached 20,000, and included 10 artillery battalions.
St Malo was extensively damaged during 6 and 7 August. On the afternoon of 6 August many fires broke out across the town. French civilians believed that these were accidentally started by German troops who were burning codebooks and other documents, and that SS personnel both refused to allow firefighters to put them out and lit additional fires. Efforts to fight the fires were also complicated by the fact that the town’s water supply had been cut by the Americans on that day in an effort to induce the garrison to surrender. A Kriegsmarine patrol vessel was scuttled in the harbour during 6 August. On the morning of 7 August the Germans completely destroyed St Malo’s harbour with explosives, and in response US artillery began to shell the town. The German demolitions and US bombardments resulted in fires that burned for the next week.
von Aulock ordered the arrest of all French males aged between 17 and 70 who had remained in St Malo as hostages following an inaccurate report that civilians had attacked his troops. The 382 hostages were held in harsh conditions at Fort National, and denied shelter, food and water, and when US mortar fire struck the fort, 18 of the hostages were killed.
The 83rd Division continued to advance slowly toward St Malo between 7 and 9 August. The 330th Infantry found that the German strongpoint at St Joseph’s Hill in the centre of the division’s sector was impossible to attack only with infantry. This position was a quarry that had been converted into a fortification through the addition of tunnels and bunkers. After a two-day artillery bombardment, the 400 survivors of the German garrison surrendered on 9 August. After this position fell, the division was able to move rapidly toward the town. On the left of the division’s sector, the 329th Infantry captured St Servan sur Mer and reached the Citadel. On the right of the sector, the 331st Infantry secured Paramé and cut off the garrisons of St Ideuc and Fort la Varde. By the end of 9 August, the 83rd Division had taken some 3,500 prisoners but still faced German forces in a host of fortified positions.
Free French forces surrounded Dinan on 6 August and found that several hundred Germans had remained in the town. The Germans were unwilling to surrender to Free French troops, but indicated that they would do to Americans. On 7 August the 121st Infantry crossed the Rance river to begin its advance on Dinard, and a party from this unit took the surrender of the Germans at Dinan. As it advanced to the north from Dinan, the 121st Infantry found that all roads in the region were heavily defended. The German positions comprised roadblocks, well camouflaged strongpoints, minefields and pillboxes, all supported by artillery fire. Progress was therefore slow, and it took until the afternoon of 8 August for the 3/121st Infantry to capture the village of Pleurtuit, 4 miles (6.4 km) from Dinard. Soon after the capture of Pleurtuit, StuG III assault guns, supported by infantry, launched an attack that cut the roads to the village and isolated the 3/121st Infantry. Attempts by the 1/121st Infantry to break through were unsuccessful. Macon judged that the 121st Infantry’s performance had been indifferent and that there was therefore a need to reinforce it. He decided to give priority to the capture of Dinard after St Joseph’s Hill had been secured to rescue the isolated battalion, the elimination of the German artillery in the area and the prevention of St Malo’s garrison from escaping across the Rance river. Macon therefore transferred the 331st Infantry to the Dinard sector and took personal control of operations there.
The two US regiments began their attack on Dinard during 11 August. German resistance remained stubborn, and little progress was made on that day. On the following day Bacherer, the German commander in the Dinard sector, rejected a demand from Macon that he surrender and stated that he would fight 'for every stone'. The 331st Infantry finally broke through German positions near Pleurtuit during the afternoon of 12 August, and rescued the 3/121st Infantry. During the period it was isolated, the battalion had fought off several German attacks and suffered the loss of 31 men killed and 106 wounded.
The US troops continued their attacks on 13 August with a programme of isolating and destroying individual pillboxes. Both regiments entered Dinard the next day. The Dinard position was destroyed on 15 August, the Americans securing the town and nearby villages. Almost 4,000 Germans, including Bacherer, were taken prisoner.
The balance of the 83rd Division had continued its advance on St Malo during the attacks on the Dinard area. These operations were commanded by the division’s assistant commander, Brigadier General Claude Birkett Ferenbaugh while Macon was focused on the Dinard operation. While it was no longer considered feasible to bring St Malo’s harbour into useful service, it was believed to be necessary to capture the fortifications in the area to prevent German artillery from attacking Allied shipping using nearby ports. This would also make the 83rd Division available for other tasks. The Americans also hoped that securing the town would encourage the German garrisons of other isolated ports to surrender.
Before the walled town and the Citadel were attacked, it was decided to capture Fort la Varde and St. Ideuc, whose garrisons were able to provide mutual support. One of two battalions under the control of the 330th Infantry began the attack on the St Ideuc position on 9 August. After three days of artillery bombardments and infantry attacks, first on pillboxes and then the position itself, St Ideuc’s 160 surviving defenders surrendered on the afternoon of 12 August. The battalion immediately began attacking Fort la Varde, whose 100 remaining defenders also surrendered on the evening of 13 August.
The other battalion under the 330th Infantry attacked toward St Malo with the goal of capturing the causeway that linked the town to Paramé. This led to house-to-house fighting in which the US infantry advanced with support from tanks, tank destroyers and engineers. The ruins of St Malo’s casino were captured on 11 August, and the US forces were then faced with the challenge of crossing the exposed 1,000-yard (915-m) causeway to assault the well-defended château on the landward side of St Malo. The château was bombarded by artillery and air attacks for two days, with little apparent effect on the defenders. A truce was agreed for the afternoon of 13 August to allow some 1,000 French civilians as well as 500 hostages and internees who were being held by the Germans at Fort National to be evacuated. The 330th Infantry assaulted St Malo on the morning of 14 August. Under the cover of an intensive artillery bombardment and a smokescreen, a battalion charged across the causeway and entered the walled town. The few Germans in the town were quickly captured, but the château held out until the afternoon when its defenders surrendered; 150 men were taken prisoner. On 16 August US infantry assaulted Fort National and Grand Bey, which were the last remaining German positions on the mainland of the St Malo area other than the Citadel. Fort National was found to be unoccupied, and the 150 defenders of Grand Bey surrendered after a brief fight.
The Citadel was a formidable position. It had been upgraded by the addition of interconnected blockhouses to improve the defences of the Fort de la Cité d’Aleth. The thick walls were almost impervious to air attacks and artillery, and it had large quantities of water, food and other supplies. The garrison was weakly armed, with only 18 or 20 machine guns and a few mortars, but these weapons had been skilfully sited to maximise their effectiveness. From an early stage of the battle, Macon had been aware that it would be difficult to neutralise the Citadel.
US artillery and Allied aircraft began to attack the Citadel during the assault on St Malo. Shortages of ammunition disrupted the artillery bombardments and the air attacks proved ineffective. Attempts by a US psychological warfare unit to persuade the Germans to surrender were unsuccessful, and von Aulock also rejected entreaties from a captured German chaplain and a female French civilian with whom he had a close relationship. His refusal to surrender and the hardline orders he issued led to his receipt of the nicknamed 'mad colonel' by the garrison.
On 11 August, one company of the 329th Infantry, reinforced with engineers and three Free French soldiers, assaulted the Citadel after it had been attacked by medium bombers. Some of the troops reached an interior courtyard in the fortification, but withdrew after finding that the bombardment had not breached the main defences. Artillery attacks continued over the next few days, and two specially trained 96-man strong assault groups made another assault on 15 August after medium bombers had struck the Citadel once again. This attack was repelled by machine gun fire.
After the unsuccessful 15 August assault, Macon ordered an intensification of the artillery bombardment. Two 8-in (203-mm) guns were positioned less than 1,500 yards (1370 m) from the Citadel to target individual portholes and vents. Mortar bombardments also increasingly used white phosphorus incendiary and smoke rounds. An air attack using napalm incendiary bombs was planned for the afternoon 17 August: this was to be one of the first times napalm bombs were used in combat. Shortly before the time for which the air attack was scheduled, a white flag appeared over the Citadel and a party of German soldiers emerged from it to inform the Americans that von Aulock wished to surrender. The air attack was then diverted to attack Cézembre, and von Aulock and 400 other Germans were taken prisoner. von Aulock gave the destruction caused by the 8-in (203-mm) guns and a collapse in the garrison’s morale as his reasons for surrendering. The surrender marked the end of all German resistance in the St Malo area aside from the Cézembre garrison that continued to hold out. By this time the 83rd Division had captured more than 10,000 prisoners, and its own casualties had been relatively light.
The 83rd Division, less two battalions of the 330th Infantry, were withdrawn from St Malo after von Aulock’s surrender. The main body of the division undertook largely defensive tasks south of Rennes to allow the troops a period of recuperation. The two battalions remaining at St Malo formed a garrison, and sought to prevent the Germans at Cézembre from landing on the mainland. Following the surrender of St Malo the German warships that had been operating in the Gulf of St Malo rarely put to sea.
Allied bombers attacked the German positions on Cézembre during 6 and 11 August, and the VIII Corps' artillery began to bombard the island from 9 August. Following von Aulock’s capitulation and the napalm attack, Macon sent a party to Cézembre on 18 August to request its surrender. The garrison commander, Oberleutnant Richard Seuss, refused to do so on the grounds that he was under orders to continue resistance and still had ammunition. The Americans observed that the German positions appeared to have been badly damaged by the bombardments. Another air raid was conducted against the island on 23 August. German minesweepers and other small vessels transported ammunition from the Channel Islands and evacuated wounded personnel on most nights from 17 August onwards.
No further attacks were made against Cézembre for another week, after which it was decided to eliminate this German position. The decision may have resulted from intelligence gained from three Italian deserters who fled to St Malo late in August and described the heavy damage to the island’s defences and told of water and ammunition shortages. The 330th Infantry was instructed to begin preparations for an amphibious assault, and to transport the troops, 15 LCVP landing craft of the US Navy were moved to St Malo by truck from 'Omaha' Beach in Normandy. Air attacks resumed on 30 August. A large attack involving 300 heavy bombers, including British Avro Lancaster four-engined heavy bombers as well as 24 Lockheed P-38 Lightning twin-engined fighter-bombers armed with napalm was made on the next day. Artillery bombardments also targeted the island’s water tanks. To assist the members of the garrison who had been wounded in these attacks, the hospital ship Bordeaux and a barge were despatched from the Channel Islands, but both vessels were captured by Allied naval forces. Once again, Seuss refused to surrender during another truce on 31 August.
A major air and naval attack took place on 1 September. US and British twin-engined medium bombers attacked the island, followed by 33 napalm-armed Lightning fighter-bombers. A British battleship and US artillery then shelled Cézembre. Another message was transmitted to Seuss requesting that he surrender, but he refused. After an attempt to use small craft to evacuate the garrison on the night of 1/2 September had been foiled by bad weather, Seuss received authorisation to surrender from his superior officer in the Channel Islands. At 19.30 on the next day, as the 330th Infantry was preparing to attack, a white flag appeared over the island and Seuss capitulated. The US landing craft evacuated the 323 surviving members of the garrison, including 12 female nurses. Seuss gave the destruction of Cézembre’s water-distillation plant as his reason for surrendering. Despite the extent of the attacks on the island, the garrison suffered only light casualties.
The 'Battle of St Malo' had mixed results. While the 83rd Division had performed well, but the German garrison had also achieved its goals. von Aulock had denied St Malo’s port to the Allies and, by detaining the 83rd Division and other VIII Corps units for two weeks, prevented the Americans from being able to take rapid and decisive action against the German positions at Brest and Lorient. The battle also occupied Allied aircraft that were needed to support the advance into northern France.
The VIII Corps assaulted and captured Brest in a battle which lasted from 7 August to 19 September. The Germans also demolished the city’s port, and it proved impractical to restore it to service. The rapid liberation of France and the capture of ports on the English Channel reduced the potential value of the remaining German-held cities in Brittany and the French Atlantic coast to the Allies. On 7 September, Eisenhower approved a proposal that these positions be contained rather than attacked. French units and a US division besieged them for the remainder of the war. As result, Cherbourg in Normandy and Brest and St Malo in Brittany were the only fortified German-held ports in France to be taken by the US Army. British and Canadian forces also captured Antwerp, Dieppe, Le Havre and Rouen during 1944, and besieged several other fortified ports in northern France until the end of the war.
The US Army’s Communications Zone began work on reopening the ports of the St Malo area on 25 August. Cancale was soon judged unsuitable as a result of unfavourable tidal conditions, and was dropped from the plans. While the logisticians initially believed that there were good prospects for bringing St Malo’s port facilities back into service, the extent of the damage frustrated their efforts. After a report completed in September revealed that the Canal d’Ille et Rance, which links the Rance river and Rennes, was in a poor condition, it was decided that the reopening of St Malo as a port was not worth the effort. On 21 November the town was handed over to the French.
St Malo suffered extensive damage during the battle: 683 of the 865 old town buildings were destroyed.