This was a British naval and military mopping-up operation on the southern half of Abadan island in Iran during 'Countenance' (25 August 1941).
The operation was planned as the means of taking five German and four Italian merchant ships at Bandar Shahpur, together with the port itself as this latter was of great importance as the terminal port of the Trans-Iranian Railway. The operation was simultaneous with a combined operation to capture Abadan as far south as Ahwaz.
The naval and army units which took part in 'Bishop' was Force 'B', commanded by Captain G. H. Adams in the armed merchant cruiser Kanimbla. The other ships included the Indian sloop Lawrence and Investigator (ex-survey vessel), British corvette Snapdragon, ex-Yangtze river gunboat Cockchafer, Anglo-Iranian Oil Company tugs St Athan and Delaver, British armed trawler Arthur Cavanagh, one dhow, one RAF picket boat, and two companies of the 3/10th Baluch Regiment.
The general plan of the operation was completed before the arrival of Kanimbla in the Persian Gulf, and it was clear right from the beginning that the use of so mixed a force demanded careful training if the object of capturing the merchant ships was to be achieved. Fortunately it was possible to train boarding parties with a fair degree of secrecy in an open anchorage 11 miles (17.7 km) from the nearest land off the entrance to the Shatt al-Arab waterway despite the fact that weather conditions were sometimes bad for boats. The dhow and the RAF launch also suffered damage. Among the steps taken to preserve secrecy was a ban on ships returning to the Shatt al-Arab. Efforts were made, through the use of painted canvas, to make Kanimbla look as much like a passenger ship as possible. So successful were these precautions that it seemed unlikely that even in the bazaar there was any hint that the large 'troop ship' in the offing was the mother ship for a force about to capture the port and the German and Italian ships in Bandar Shahpur.
Eight boarding parties were required, three of which were provided by the Snapdragon, Cockchafer and Lawrence, and the other five by Kanimbla. The boarding parties were organised on similar lines, and consisted of upper-deck and engine-room groups whose guiding principle was that men boarding must always work in pairs and work quickly.
Lawrence was informed by Adams that she should make every endeavour to capture the Iranian gunboats without firing, which in the event she did. Similar instructions were given to all elements of the force in relation to the floating dock, in case any of them were subsequently detailed to lake it. Cockchafer also took this dock without a shot being fired.
Lawrence embarked a detachment of 3/10th Baluchis at Basra at 16.00 on 10 August. The detachment consisted of A and D Companies, in all 10 officers and 256 other ranks. At 20.30 the vessel departed the jetty and steamed quietly down the Shatt al-Arab to rendezvous, at 11.00 on 11 August, with Kanimbla out of sight of land, and there transferred the army detachment. Between 11 and 16 August Force 'B' underwent intense training, and on 16 August Adams was able to report that training had been completed. Between 16 and 25 August, when the operation took place, the intensity of the training was eased. On the night of 23 August orders were received that the operation would begin at 04.10 on 25 August.
All the vessels were berthed alongside Kanimbla by 12.00 on on 24 August, when final instructions were issued. The dhow was first to sail at 13.32, the RAF launch an a tug at 15.00, and the remainder of the force at 20.15. In addition to reconnaissance, the dhow and the RAF launch were provided with hurricane lanterns which they were to attach to any unlighted buoys they found in the Channel of Khor Musa, but in the event all the buoys and beacons were alight. The dhow kept Adams fully informed by radio of all navigational matters including the characteristics of the lights which were did not accord with the chart.
Undertaken in good visibility and essentially to schedule, the passage up the Khor Musa was uneventful, Kanimbla leading with a tug on each side of the bow. Astern of her were Cockchafer, Lawrence, Snapdragon and Arthur Cavanagh. On reaching buoy 13 at 13.15, Kanimbla dropped back in accordance with the plan. The ebb-tide was then at least 2 kt, so all units were ordered to proceed at 10 kt. The RAF launch and Arthur Cavanagh could not make this speed, however, and were therefore late in reaching their objectives. Lawrence now forged ahead, overhauling the two tugs and Cockchafer, and at 04.15 reached and boarded the Iranian gunboats Karkass and Chanbaaz. Surprise was total and there was no resistance, and by 04.30 both gunboats had been secured and their crews placed under guard. A floating dock belonging to the Iranian government was captured intact by the Cockchafer.
Meanwhile, the Axis merchant ships, which had been prepared for scuttling, received an alarm. Explosions were heard and fires were seen to break out almost simultaneously in the three Italian ships and two of the German ships. This was the sight which awaited Kanimbla as she turned into the straight in the wake of the flotilla. Two US ships were berthed in the available space by the jetty, so Kanimbla steered straight for the Italian tanker Bronte, which was blazing fiercely amidships, while Lawrence left prize crews aboard the captured gunboats and made for Caboto, which she captured and then put a party on board to fight the fire. She then went alongside Barbara and used hoses and a bucket chain to deal with a fierce fire under her bridge. The fires on both ships had been extinguished by 07.45.
With all hoses rigged, Kanimbla poured water into the Bronte, which was filled with stacks of kerosene tanks that were exploding. A foothold was obtained after the first rush of flames had been beaten back, and in some three hours the ship was saved. Kanimbla was lacking 16 officers and 111 men away on boarding parties round the harbour, and the fire on Bronte was fought and defeated by the few crew remaining.
The German ship Weissenfels was lost. The German preparations had been very efficient, and it seems that the chief engineer of Weissenfels had taken action to scuttle and fire his ship before the alarm came from Hohenfels.
The situation ashore at 17.00 on 25 August was calm, and afloat the situation was that Marienfels and Wildenfels were anchored and apparently ready to be brought forward. Sturmfels was at anchor, with one of her holds full of still-smouldering corn that was soaked with firefighting water and might swell and burst the bulkheads. There was also the fear that the fire might spontaneously ignite Barbara, Caboto and Bronte. Hohenfels was beached. Weissenfels was still burning furiously, all oil fires apparently out but in a condition in which it was impossible to get into the vessel and shut valves, so she sank in deep water at 05.00 on 26 August.
There were no British or Indian casualties, and the seven captured Axis merchant vessels (the German Wildenfels, Sturmfels and Marianfels, and the Italian Caboto, Bronte, Hilda and Barbara) were taken first to Basra and thence to India, which they reached in September 1941.