'Credential' was a British naval sweep for German transport vessels and invasion craft delivering forces to attack British positions or to reinforce their own garrisons on the islands of the Aegean Sea (7/9 October 1943).

The context for this and other similar naval undertakings in the Aegean Sea campaign, which led to significant losses, was provided by Allied armistice with Italy, agreed on 3 September 1943 but announced only on 8 September for implementation on the following day. One of the immediate consequences of this Italian defection from the Axis camp was the Dodecanese campaign, which was an ill-starred British attempt to capture the Italian-occupied Dodecanese islands for use as bases against the German-controlled Balkans. The British effort, which had limited US air support, failed and the entire Dodecanese islands group fell to the Germans within two months.

Lying on the south-eastern part of the Aegean Sea, the islands of the Dodecanese group had been in Italian control since the Italo-Turkish War in 1911. During Italian rule, the strategically well-placed islands became a focus of Italian colonial ambitions in the eastern part of the Mediterranean and Rhodes, the largest of the islands, was developed as a major military and aerial base. The island of Léros, with an excellent deep-water port of Lakki (Portolago), was transformed into a heavily fortified seaplane base.

After the fall of Greece in April 1941 to the German 'Marita' and the Allied loss of the island of Crete in May of the same year to 'Merkur', the whole of Greece and its many islands were occupied by German and Italian forces. With the ultimate defeat of Axis forces in North Africa in spring 1943, Prime Minister Winston Churchill, who at least as far back as the Gallipoli campaign of 1915/16 had been fascinated by the strategic possibilities of the region, turned his sights on the islands. The British envisaged an operation to capture the Dodecanese islands and Crete in undertaking which would deprive the Axis powers of excellent forward bases in the Mediterranean, and also serve to apply pressure on neutral Turkey to join the war on the Allied side and thus fulfil one of Churchill’s most cherished concepts, namely the opening of a 'route through the Dardanelles to Russia as an alternative to the Arctic Convoys'.

At the 'Symbol' conference in Casablanca in January 1943, the initial go-ahead was given, and Churchill ordered a start to be made on the drafting of initial plans on 27 January. The 'Accolade' plan called for a direct attack on Rhodes and Kárpathos, with forces totalling three divisions, an armoured brigade and supporting units. The notion of landing on Crete, which was too well fortified and had a strong German garrison, was abandoned. The main problem faced by the British planners was how to counter the warplanes of General Martin Fiebig’s X Fliegerkorps, which were based close to the islands, whereas Allied aircraft had to operate at considerably longer range from bases in Cyprus and the Middle East.

The whole undertaking was also rendered more difficult by the demands of the altogether more important 'Husky' (i) invasion of Sicily scheduled for July 1943. The Americans were also sceptical about the feasibility of Dodecanese island operations, suspected that this was designed to further British post-war political ambitions in the region, and saw them as an unnecessary diversion from the main front in Italy. Therefore the Americans refused to support Dodecanese island operations, and warned the British that they would have to rely on their own resources.

As an Italian surrender became increasingly possible, in August 1943 the British started preparations to take rapid advantage of a possible Italian defection by launching a scaled-down 'Accolade'. The assembly of a force based on Major General D. Russell’s Indian 8^th Division was started, and limited US assistance in the form of Lockheed P-38 Lightning twin-engined long-range fighter squadrons, was requested. As a result of the 'Quadrant' conference in Quebec during August 1943 and the continued US refusal to provide air support, the forces and ships earmarked for 'Accolade' were diverted to other fronts, barely a week before the Italian armistice.

As this was announced, the Italian garrisons on most of the Dodecanese islands wished either to change sides and fight with the Allies or merely to return home. Anticipating the Italian defection, however, German forces, based largely in mainland Greece, had been rushed to many of the islands to gain control. These German forces were part of Heeresgruppe 'E' commander by Generaloberst Alexander Löhr.

The most important German force in the Dodecanese islands was the 7,500-strong Sturmdivision 'Rhodos' commanded by Generalleutnant Ulrich Kleemann. This had been created during the summer on the island of Rhodes, the administrative centre of the Dodecanese islands group and the location of three military airfields. Because of this, Rhodes was the principal military objective for both the Allies and the Germans.

On 8 September, the Italian garrison on the island of Kastelorizo surrendered to a British detachment, which was reinforced during the following days by ships of the Allied navies. On 9 September a British delegation was dropped by parachute on Rhodes in order to persuade the Italian commander, Ammiraglio di Squadra Inigo Campioni, to join the Allies. The swift action of the German forces, however, pre-empted the Allies. Without waiting for the Italians to decide, Kleemann attacked the 40,000-strong Italian garrison on 9 September, and forced it to surrender by 11 September. The loss of Rhodes dealt a critical blow to Allied hopes.

While the Italian government had surrendered and many Italian soldiers were tired of war and had become opposed to Mussolini, Italian Fascist loyalists remained allied to Germany in the Greek campaign, with Generale di Divisione Mario Soldarelli, commander of the 6a Divisione di fanteria 'Cuneo', rallying Fascist 'Blackshirts' and soldiers loyal to Benito Mussolini to continue the war in support of Mussolini’s aims, and German forces in Greece convinced 10,000 Italians in the Aegean to continue to support their war effort.

Despite this setback, the British continued with the occupation of several other islands, including the three larger islands of Kos, Samos and Léros on the presumption that the Germans were overextended in the Aegean and that the British themselves had a decided naval superiority at sea, and could provide Kos with air cover with the Supermarine Spitfire single-engined fighters of two squadrons.

It was hoped that from these islands, and with Italian co-operation, an assault on Rhodes could be eventually launched. Between 10 and 17 September mixed British and Greek forces secured the islands of Kos, Kalymnos, Samos, Léros, Symi and Astypálaia, supported by British and Greek warships.

The Germans responded with considerable speed, and by 19 September Kárpathos, Kasos and the Italian-occupied islands of the Sporades and Cyclades groups were in German hands. On 23 September, Generalleutnant Friedrich-Wilhelm Müller, commander of the 22^nd Division garrisoning Crete, was ordered to take Kos and Léros.

With the single airfield on Kos identified as the key to the British ability to resist a German assault, from 18 September the X Fliegerkorps began to bomb the airfield and also the British positions on the island. At the same time, air reinforcements started to arrive in Greece, and by 1 October the Germans had 362 operational aircraft for Aegean service.

The British forces on Kos numbered about 1,500 men (only 680 of them infantrymen) and about 3,500 Italians of Generale di Divisione Michele Scaroina’s 50a Divisione di fanteria 'Regina'. On 3 October, the Germans launched their 'Eisbär' (v) amphibious and airborne assault, and reached the outskirts of the island’s capital later on the same day. The British withdrew under cover of night and surrendered on the next day. The fall of Kos was a major blow to the Allies, since it deprived them of vital air cover for the rest of the Dodecanese campaign.

The task of supporting the British operations in the Dodecanese islands group was the responsibility of Admiral Sir John Cunningham’s Levant command, which now had, as well as large numbers of smaller craft, 17 'Hunt' class escort destroyers. As a result of their short range, however, these were not ideally suited to the tasks demanded of them. On 30 September the British learned that the Germans were assembling shipping and landing craft at Piraeus and in Cretan harbours, and were embarking troops and equipment. In anticipation of a German movement toward Rhodes or Léros, three destroyers were despatched from Alexandria to patrol to the east of Crete. During the evening of 2 October a convoy was sighted by aircraft farther to the north, off the island of Naxos, but by that time the destroyers had been forced to return to refuel. Two submarines were ordered to intercept the convoy off Kos, which was now seen as the convoy’s most probable destination: the submarines did not arrive in time to effect an interception. The British headquarters on Kos received reports of the German convoy’s progress, but assumed that the convoy was bound for Rhodes.

At 05.00 about 2,000 German troops started to disembark on Kos, covered by heavy air bombardments, and successful parachute landings quickly followed. The British garrison was now heavily outnumbered, and to hold the harbour and the airfields (a second had been improvised) was beyond its strength. After the withdrawal of the British surface ships the only counter-action immediately possible was from the air by the attacks of Bristol Beaufighter twin-engined long-range heavy fighters operating from Cyprus. Many attacks were made on German shipping during the day, but these did not adversely affect the landing to any major degree, and substantial losses were suffered by the Beaufighter warplanes. By the evening of 4 October the British resistance on Kos had ended.

The Germans next began energetically to prepare their 'Leopard' (iii) counter-invasion of Léros, and as they had already deprived the British of the only airfields from which, poor though they were, single-engined fighters might have operated, their prospects of further success were good.

British naval reinforcements, consisting of four ships of the 12^th Cruiser Squadron under Commodore W. G. Agnew in Aurora, the anti-aircraft cruiser Carlisle and eight more large destroyers, had meanwhile been ordered to the Aegean from the central Mediterranean, but reached the area too late to have any effect on the battle of Kos. By this time it was clear that the failure to intercept the German invasion convoy and the overwhelming German air superiority were the factors primarily responsible for the defeat on Kos. If the naval reinforcements had been sent earlier, and if adequate fighter cover been available, it would have been impossible for the Germans to transport their assault force.

There was also another factor which had affected the naval strength available at a critical time. The battleships Howe and King George V had reached Alexandria on 16 September, having escorted some of the surrendered Italian major warships from Malta. The six fleet destroyers which had accompanied them were at once sent to strengthen the forces operating in the Aegean Sea but when, on 1 October, the two British battleships returned to the west, four of the destroyers sailed with them as escorts.

Meanwhile the Germans had been increasing their strength on Kos with the object of attacking Léros, whose the British garrison totalled just 1,100 men. On the night of 6/7 October the light cruisers Sirius and Penelope and two destroyers were operating in the Aegean, and early on 7 October they intercepted a German convoy of an ammunition ship and six ferry barges, off Stampalia. A battalion of troops intended to reinforce Kos was embarked in the convoy, but only one barge survived the British ships' attack. More than 400 men and the whole of the German battalion’s equipment were lost. After achieving this success the squadron withdrew by the Strait of Scarpanto, in which it came under heavy air attack. At first US Army Air Forces' Lightning long-range fighters gave effective cover, but when these had to turn back the relief air escort failed to find the ships. Penelope received a hit in a heavy attack by 18 Junkers Ju 87 single-engined dive-bombers, and was further damaged by several near-misses, but the bomb which did hit the light cruiser failed to explode, and Penelope got back to Alexandria safely.

Two days later, in 'Persecution', the light anti-aircraft cruiser Carlisle and initially the destroyers Panther and Petard, covered initially by a single Beaufighter, were carrying out out a sweep of the Strait of Scarpanto. The ships were later joined by the destroyers Aldenham and Free Greek Themistokles which, on the following day, were replaced by the destroyers Rockwood and Free Greek Miaoulis. On 9 October Carlisle came under attack by a large force of Junkers Ju 87 dive-bombers while in company with Panther and Rockwood. Despite the arrival of seven P-38 fighters, which shot down eight of the German aircraft as they returned to Rhodes, and also made offensive sweeps over Crete and Léros, and attacked the airfield on Kos.

The anti-aircraft cruiser took four direct hits and several near misses, resulting in extensive structural damage and flooding, as well as the deaths of 20 and wounding of 17 of the ship’s crew. Panther was sunk, and Carlisle was towed back to Alexandria by Rockwood.

On 10 October the US fighters were recalled to the central Mediterranean, which ended the period of relief they had afforded to the British naval forces in the Aegean. By the middle of October, therefore, Penelope of Agnew’s force and Carlisle had been damaged, but the arrival from Malta of Phoebe had restored the British strength to four ships. On 17 October, however, Sirius was hit by a bomb. There were now eight fleet destroyers available for the Aegean, but of the 17 'Hunt' class escort destroyers of the Levant command, headed since 14 October by Vice Admiral Sir Algernon Willis, only eight were still available for one reason or another.

Several submarines and coastal craft, as well as an assortment of vessels of the Levant Schooner Flotilla, which were used to deliver men and supplies between the various islands, and to and from the Turkish mainland, completed the British naval strength in the Aegean. The larger surface ships continued to make forays into the Aegean from Alexandria, but on 15 October Willis reported that naval patrols could not be continued by day without suffering prohibitive losses, and in this he was supported by Air Chief Marshal Sir William Sholto Douglas, the British air commander in the Middle East. Despite of the pessimistic view of the naval and air commanders, the British decision to attempt to hold Léros was not changed, so stores and reinforcements were delivered by destroyers and submarines. The British plan was thus to strengthen the garrison sufficiently to hold the island throughout the winter, and then to maintain the garrison by caiques working from Samos.

In October the destroyers Jervis, Penn, Pathfinder and Petard each made two trips to Léros, and six other British and Greek destroyers each made one trip. Heavy losses resulted, however. On 22 October the Greek destroyer Adrias struck a mine and was severely damaged, and when Hurworth went to her assistance she too was mined and sank with heavy loss of life. Adrias managed to beach herself on the Turkish coast, and finally reached Alexandria under her own steam, but minus her bow, on 6 December. Two days after the ming of Adrias and Hurworth, the destroyer Eclipse, with 200 soldiers on board, was mined in the same waters; the survivors were rescued by Petard, but Captain P. Todd, commodore of the Levant destroyer flotillas, was lost.

On 24 October a supply ship was bombed and sunk in the harbour at Samos, and four days later an LCT carrying guns and troops was also sunk. These and other losses prompted Willis to send a pessimistic report to London, highlighting the adverse operation conditions and anticipating heavy destroyer losses as and when the German attacked Léros, largely as a result of the Germans' overwhelming air superiority.

On 30 October Aurora and three destroyers from Alexandria entered the Aegean to make another offensive sweep against German shipping, and soon came under air attack. Escorting Beaufighter aircraft could not prevent the cruiser from being hit and damaged, with heavy casualties, but the ship managed to reach Alexandria safely, escorted by one destroyer, while the other two carried on into the Aegean. Next the escort destroyer Belvoir was hit, but the bomb did not explode.

The naval forces available in the Levant were now so reduced that it was very difficult for the surviving ships to continue the reinforcement of Léros, let alone press ahead with offensive sweeps and patrols. The Chiefs-of-Staff Committee in London now suggested that the use of cruisers and destroyers was too expensive, and Sir John Cunningham, now commanding the naval forces in the entire Mediterranean theatre, was reluctant to release more from the central Mediterranean, where major operations were under way in Italy and the waters round it.

Between 5 and 10 November the Germans began to move their landing craft gradually to the east from Greece. The British struck at these from the air, but the Beaufighter was by no means ideally suited for such work, and the aircraft therefore inflicted little damage but themselves suffered heavy losses. Nor were the destroyers sent to intercept the convoy any more successful. In daylight the German craft lay up in various harbours under strong air cover, and when they moved by night they were very hard to find. By 10 November the Germans had successfully assembled a substantial fleet of some two dozen small craft at Kos and Kalino. Two naval squadrons, each of three destroyers, bombarded the harbours of those islands on the night of 10/11 November to minimal effect. Then, as was by now standard, the arrival of daylight saw the start of air attacks as the destroyers were withdrawing, and Rockwood was hit by a glider bomb.

One of the two destroyer forces had anchored off the Turkish coast on 11 November, and its three ships remained there all the next day despite receiving air reports of German craft heading for Léros during the early part of the morning. These were actually carrying the German 'Leopard' (iii) invasion force to land on the northern side of Léros. Even though the destroyers' senior officer was concerned by a shortage of fuel, and knew that more destroyers could not arrive until the next night, it now seems that he should have taken his ships on patrol earlier. Not until after the fall of night on 12 November did he sweep the waters around Léros, but by that time the Germans had landed. So it was that the British, having watched the movement of the German invasion force right across the Aegean from Piraeus to Kos, failed to intercept it on its final stage.

On the night of 12/13 November, after the first German landings, destroyers and motor torpedo boats swept the adjacent waters for German reinforcements but located none. Three other destroyers were now on the way to the Aegean, but very early on 13 November one of these, Dulverton, was hit by a glider bomb and sunk. The other two lay up in Turkish waters before sweeping around Léros and bombarding shore targets after dark. On the same day the Germans managed to reinforce their strength on Léros by sea and air.

The British tried to reinforce the garrison of Léros from Samos, but very bad weather frustrated the first attempt. On the night of 13/14 November, however, three more destroyers arrived in the Aegean, and during the next two nights Echo and smaller vessels managed to carry 500 troops from Samos, and also sank three German landing craft which were approaching Léros full of troops.

Slow signalling and slow reaction by a British destroyer prevented the interception of German reinforcements on the night of the 15/16 November, and by dawn on 16 November the British situation on Léros had become critical, the last of the garrison surrendering later on the same day.

Immediately after the fall of Léros the British decided to evacuate the British and Greek troops remaining on Samos, and this was carried out during the night of 19/20 November. Most of the garrison of Kastelorizo was evacuated on 28 November. The Germans interfered with neither of these undertakings.

Thus ended a series of fruitless operations whose cost to the British was considerable. The British and Greek navies had suffered damage to four cruisers (Carlisle irreparably), six destroyers had been sunk and four others damaged, and two submarines and 10 coastal craft and minesweepers had been lost.