The 'Battle of the Mons Pocket' was an engagement fought between Allied and German forces, and as such formed part of the final stages of the rapid Allied advance across France and into Belgium (31 August/5 September 1944).

During the battle US Army forces, assisted by the Belgian resistance, encircled a large number of retreating German army and Waffen-SS troops near the town of Mons in Belgium. The German forces were disorganised and unable to counter the Allied forces. Around 3,500 Germans were killed and 25,000 made prisoners of war. Allied casualties were light.

Late in July and during August 1944, Allied forces broke out of their 'Overlord' lodgement in Normandy and advanced rapidly across north-eastern France. The primary goal of the Allied forces at this time was to advance quickly enough to reach the Rhine river before the Germans could man and reactivate the 'Siegfried-Linie' defences which ran along the border between France and Germany. On 27 August Lieutenant General Omar N. Bradley, commander of the 12^th Army Group which was the main US Army formation in northern France, ordered the armies under his command to 'go as far as practicable' until they out-ran their supply lines. The US Army was well-suited to this type of warfare as its formations and units were highly motorised and trained to conduct large-scale mobile operations.

The German forces in France had suffered heavy losses during the fighting in Normandy, and attempted to fall back ahead of the Allied forces. Their ability to do so was limited by the speed of the Allied advance, road congestion, destroyed bridges and Allied air attacks. The German infantry units were considerably less mobile than their Allied equivalents as they lacked large quantities of motor transport. At the start of the Allied break-out, Adolf Hitler ordered that defensive positions be prepared along the Somme and Marne rivers in northern France for the fighting of delaying actions. By the time the German forces reached the defensive positions along the Somme and Marne rivers, however, they were in no any sort of condition to offer serious resistance: a US Army history of the campaign described the German units at this time as 'exhausted, disorganized, and demoralized'. By a time late in August, the German forces in northern France and Belgium were therefore retreating in disarray. The Oberbefehlshaber 'West', Generalfeldmarshall Gerd von Rundstedt (from 17 August Generalfeldmarschall Walter Model), was attempting to re-establish a coherent line along the Scheldt river’s estuary, the Albert Canal and the Meuse (Maas) river.

Late in August, Bradley decided that Lieutenant General Courtney H. Hodges’s US 1^st Army should, at least on a temporary basis, prioritise cutting off the retreat of German units in northern France and Belgium over reaching the Rhine river. Hodges was therefore instructed on 31 August to advance to the north in order to cut the road linking Lille and Brussels. Hodges’s main objective was the town of Tournai in Belgium, which he was ordered to liberate by 00.00 on 2/3 September. Hodges assigned to the task to Major General Charles H. Corlett’s US XIX Corps, which was responsible for the northern parts of the 1^st Army’s area of operations. The XIX Corps reached Tournai at 22.00 on 2 September. During the advance it had taken 1,300 German prisoners. Major General Leonard T. Gerow’s V Corps, which was in the centre of the 1^st Army’s line, simultaneously advanced toward Landrecies and took it on 2 September; few German units were encountered.

SS-Oberstgruppenführer und Generaloberst der Waffen-SS Josef 'Sepp' Dietrich’s 5^th Panzerarmee was the main formation facing the Allies in northern France during the period late in August, and was responsible initially for the forces in the region from the coast of the English Channel to Paris. The 5^th Panzerarmee was wholly incapable of slowing the Allied offensive, command and control soon broke down, and the army’s headquarters at Amiens was overrun by British troops on 31 August, although Dietrich and his staff escaped.

Late in August, large numbers of German military personnel were moving through the area to the south-west of Mons. These were mostly men of General Walter Krüger’s LVIII Panzerkorps, General Erich Straube’s LXXIV Corps and SS-Obergruppenführer und General der Waffen-SS Willi Bittrich’s II SS Panzerkorps, which together included the badly battered remnants of 10 divisions as well as smaller units and many support personnel. All three corps' headquarters were out of contact with higher commands.

On 31 August the three German corps commanders decided to group their forces as a provisional army under the command of Straube, who had no sources of information about the area’s broader conditions, but was able to determine from intercepted Allied radio broadcasts and other sources that his command was in imminent danger of encirclement. In response, Straube decided to withdraw his forces to an area near Mons where canals and marshy conditions would aid his interim formation’s defensive efforts. On the following day, the German commanders decided to attempt a break-out to the north-east with the object of reaching the Nivelles area in Belgium. This would require moving their forces almost 43 miles (70 km) through the Mons area in the face of the rapid Allied advance. The main formations controlled by Straube were remnants of Generalmajor Walter Wadehn’s 3^rd Fallschirmjägerdivision, which was 'almost insignificant in numbers'; Generalleutnant Rüdiger von Heyking’s (from 3 September Oberst Harry Herrmann’s 6^th Fallschirmjägerdivision, which had a strength of about two infantry battalions plus a few larger-calibre weapons; Generalleutnant Joachim von Tresckow’s 18^th Felddivision (L) in one-battalion strength; and two infantry divisions which were 'hardly useful'. Around these forces had gathered fragmentary units, stragglers, depot personnel, and a host of miscellaneous troops. Harassed from the air, ambushed by resistance groups, attacked by Allied spearheads, finally encircled near Mons, the provisional army, with little ammunition, fuel or communications, blundered into US roadblocks and on contact was thrown into confusion.

Major General J. Lawton Collins’s US VII Corps was responsible for the eastern sector of the 1^st Army’s area of operations, and included Major General Maurice Rose’s 3^rd Armoured Division, Major General Clarence R. Huebner’s 1^st Division and Major General LouisA. Craig’s 9^th Division. On 31 August Collins was ordered to cease his corps' drive to the north-east and turn to the north toward Avesnes sur Helpe, Maubeuge and Mons. The 3^rd Armored Division led this advance, with the 1^st Division on the corps' left and the 9^th Division on the corps' right. The 4^th Cavalry Group was assigned responsibility for maintaining contact with the 3^rd Army to the south. The VII Corps initially encountered only German outposts. The 3^rd Armored Division advanced rapidly, but communications problems meant that Collins did not receive orders from Hodges on 2 September to stop short of Mons in order to conserve fuel supplies. At this time, Collins did not appreciate the size of the German force approaching Mons. The 3^rd Armored Division liberated Mons on the morning of 3 September, and at this time the 1^st Division was at Avesnes and the 9^th Division at Charleroi.

The VII Corps' advance, and that of the 1^st Army’s other two corps, trapped Straube’s forces. The 3^rd Armored Division established roadblocks on the road between Mons and Avesnes, and the 1^st Division attacked to the north-west from Avesnes into the German forces. The XIX Corps was to the west of the pocket and the V Corps to its south, and British forces were advancing rapidly to block the Germans' escape to the north. With some 70,000 men trapped in the pocket, the German forces were badly disorganised, and lacked fuel and ammunition.

There was some fighting between US and German forces on the night of 2/3 September. Within this, a tank unit of the 3^rd Armoured Division destroyed a long column of German vehicles. US air units also attacked the German forces in the Mons pocket, inflicting heavy casualties. Many of the German motorised units managed to escape from the pocket by fighting their way through the US forces. During 3 September large numbers of German troops surrendered to the Americans, however, the 1^st Division and 3^rd Armored Division between them taking some 7,500 and 9,000 prisoners.

The 3^rd Armored Division disengaged from the Mons pocket during 4 September in order to resume the VII Corps' advance to the east. The 1^st Division continued to eliminate German positions with the assistance of Belgian resistance fighters, and took large numbers of prisoners. This continued the next day, with the 26^th Infantry taking prisoner a group of 3,000 Germans near Wasmes. The 'Battle of the Mons Pocket' came to an end during the evening of 5 September.

In overall terms, some 25,000 Germans were captured in the Mons area, and German casualties included about 3,500 men killed. The remainder of the German troops, including the staffs of the three corps headquarters, escaped before the US encirclement had been completed. The Germans also lost large quantities of equipment, including 40 armoured fighting vehicles, 100 half-tracked vehicles, 120 pieces of artillery, 100 anti-tank and anti-aircraft guns, and almost 2,000 vehicles.

The VII Corps suffered few casualties. The 3^rd Armored Division lost 57 men killed, and the 1^st Division had 32 killed and 93 wounded. Losses of equipment were also light, and included two tanks, one tank destroyer and 20 other vehicles.

On 3 September, Model decided it was impossible to hold positions in northern France and Belgium, and that his forces should withdraw to the 'Siegfried-Linie'. By this time many German units were putting up nothing in the way of any fight when they encountered Allied forces.

The number of Germans taken prisoner in the Mons pocket was the second highest of any engagement during the 1944 campaign in the west, exceeded only by the capture of some 45,000 men in the Falaise pocket during August. Had the Americans advanced more quickly or their commanders understood the size of the German forces and prioritised the engagement, many more could have been taken prisoner.

The US victory in the 'Battle of the Mons Pocket' opened a gap 47 miles (75 km) wide in the German front, and thus opened the way for the 1^st Army’s advance to the 'Siegfried-Linie', as well as aiding the liberation of Belgium by the British forces. On 6 September Hodges told his staff the war would be over within 10 days if the weather held. This proved overly optimistic: logistical problems, difficult terrain, and the recovery of the German forces as they neared the national border combined to slow the Allied advance. Despite the losses at the Mons pocket, most of the German forces in north-eastern France and Belgium managed to reach Germany. By 10 September the German high command had managed to re-establish a continuous front line from the North Sea to Switzerland, and the Allies were unable to cross the Rhine river until March 1945.