Antisubmarine War WWI – Mediterranean 1916-17

Kaba departing Ryojun, 1925. She was deployed in the Mediterranean in WWI.

Japanese cruiser Akashi in drydock. Rear-Admiral Kōzō Satō commanded the “Second Special Squadron” with Akashi as flagship with the 10th and 11th Destroyer Units (eight destroyers) based at Malta from 13 April 1917. He was reinforced by the 15th Destroyer Unit with four more destroyers from 1 June 1917 to carry out on direct escort duties for Allied troop transports in the Mediterranean.

The Allies had abandoned exclusive use of patrolled routes in the Mediterranean shortly before the Germans adopted unrestricted submarine warfare. The Germans declared the great majority of the Mediterranean a Sperrgebiet (prohibited area) except for the extreme western portion off Spain, including the Balearics, and initially, the 20-mile-wide corridor to Greek waters. The Austrians promised to assist the Germans outside of the Adriatic. Their smaller submarines as they became available would now operate against Allied shipping between Malta and Cerigo. In the early part of 1917, the situation in the Mediterranean was deceptively favorable to the Allies, for in January the greater part of the Mediterranean U-boat flotilla was under repair and refit at Pola and Cattaro after the heavy demands of 1916. In January sinkings fell to 78,541 tons, only 24 percent of the total of 328,391 tons sunk in all theaters. It was the lull before the storm, for by 10 February the Germans had 10 U-boats at sea in the Mediterranean, along with an Austrian submarine, and that month submarines sank 105,670 tons of shipping. This, however, represented only 20.3 percent of the 520,412 tons sunk in all theaters, for with the introduction of unrestricted submarine warfare, the Mediterranean percentage of total sinkings inevitably declined. The successes of the Mediterranean U-boat flotilla declined again in March to 61,917 tons, just under 11 percent of the total of 564,497 tons in all theaters. April 1917 turned into a record month for the Mediterranean flotilla, just as it was a record month for U-boats in all theaters. The Germans had 14 U-boats at sea at the beginning of the month, joined by 2 Austrians. They sank in the Mediterranean 254,911 tons (3,724 tons by submarine-laid mines), or 29.6 percent of the 860,334 tons sunk in all theaters. The Austrians contributed another 23,037 tons.

The Admiralty were so alarmed by the heavy losses along the coast of Algeria, which they naturally attributed to the ineffectiveness of French patrols, that they ordered British shipping to abandon the coastal route in favor of hugging the Spanish coast from Gibraltar to Cape San Antonio and then use dispersed routes to Malta. The French, however, complained that they were using more than eighty patrol craft of all sorts on their patrolled routes in the western Mediterranean whereas the British were escorting all British troopships or ships with valuable cargoes and following routes entirely different from the French. Furthermore, the French charged that the British used their destroyers to escort troopships, leaving trawlers on the patrolled routes through British zones. These trawlers often lacked wireless receivers and could not be counted upon to divert ships from threatened areas. Admiral Gauchet, now French commander in chief, described the situation on the Malta-Cerigo route as “every man for himself.”

Allied merchant ships deliberately made use of Spanish territorial waters. This proved to be correct, if not very heroic, and it naturally added to the length and duration of a voyage. German U-boat commanders were ordered to observe the Spanish 3-mile limit, and, in fact, to avoid mistakes they were normally to observe a 4-mile limit unless there was a particularly valuable target in the fourth mile and they were quite sure of their position. On the whole, German U-boat commanders respected Spanish territorial waters and the Allies made extensive use of them. The Allies suspected the Germans were violating them, but careful analysis of sinkings generally established that the ships had strayed out of those waters when they were sunk. It was not hard to do; navigation so close to the coast could be difficult and hazardous, and merchant ship captains often were inclined to take a shortcut across the curve of a bay, which made them legitimate targets for the Germans. U-boat commanders were not angels; they obviously found more than enough targets in the Mediterranean without having to violate Spanish waters.

The Mediterranean situation could not be ignored by the Allied leaders by the spring of 1917. In early April General Sir William Robertson, chief of the imperial general staff, asked Jellicoe about a joint statement from the British naval leaders as to what reductions at Salonika would be necessary if the British were to continue the war in 1918. Jellicoe was a strong partisan of abandoning the Salonika expedition because of the strain on shipping and naval resources to support it. He recommended the immediate reduction or withdrawal of the British contingent, and he advocated a complete withdrawal if the cabinet expected the war to continue beyond 1917. This would then allow the British to recover a number of patrol craft for safeguarding commerce in home waters, free a large amount of shipping to build up a reserve of food and supply the French and Italians with coal and other necessities, and permit the British to give better protection to the sea communications with the army in Egypt. The French could be expected to strongly oppose what in their eyes was a British attempt to abandon the Salonika expedition, where France was preponderant, in favor of the pursuit of imperial gains in Palestine. An Allied conference with the Italians at St. Jean de Maurienne on 19 April took no decision on Jellicoe’s proposal, and one is inclined to believe that if the Allies did not succeed in mastering the submarine danger the issue was likely to be moot. It would then be a question of whether or not the British could continue the war.

The conflicting policies in the Mediterranean had made it obvious that another international conference was necessary. The Corfu conference took place during the crisis of the naval war. It was held in Gauchet’s flagship Provence at Corfu 28 April to 1 May. The Allies unanimously decided they would not return to the discredited system of patrolled routes created at Malta in 1916. They would navigate only by night and along coastal routes whenever possible, and those coastal routes would be patrolled along with certain strategic straits. The conference made a major change in procedure: on routes that ran far from the coast, ships would be protected by convoys and escorts following dispersed routes, that is, routes chosen by a routing officer at the port of departure according to the circumstances of the moment.

The Corfu conference had really created a hybrid system rather than one of general convoys or ships sailing independently. All ships entering the Mediterranean were now required to stop at Gibraltar for instructions and formation into convoys before proceeding to Oran, although the authorities sometimes allowed ships to navigate independently without escort if there was no submarine danger. Ships followed the patrolled coastal route between Oran and Bizerte, but they were not necessarily escorted in those waters. Ships were formed into convoys again at Bizerte for the remainder of their voyage eastward. Ships bound from Gibraltar to Marseille or Genoa continued to follow Spanish coastal waters as long as the Germans respected them.

The most important decision of the Corfu conference as far as its implications for the future were concerned was the establishment of a “Direction Générale” at Malta, which was composed of officers delegated by the different navies and was charged with the direction of everything concerning transport routes and their protection. The idea was proposed by Admiral Gauchet, but the British managed to turn it to their own advantage, for they proposed that, without modifying the present system of a French commander in chief for all the Mediterranean, all the British naval forces be placed under a single commander. The British commander in chief would have an officer of flag rank charged with protecting transport routes who would be the British representative on the Direction Générale that Gauchet had proposed. The effect of this would be to give the British the predominant role in the antisubmarine campaign. Gauchet remained the theoretical commander in chief with the largest number of dreadnoughts, seemingly preoccupied with preparing for that major naval encounter with the Austrian fleet.

The French and the Italians had by far the preponderance in capital ships, but the real action in the Mediterranean by this date was the antisubmarine war, and here the balance had quietly swung decisively toward the British. In May 1917 the total of patrol vessels of all sorts in the Mediterranean, from destroyers to sloops, from trawlers to small torpedo boats, was: British, 429; French, 302; Italian, 119; and Japanese, 8. The British had really learned that the Mediterranean was too important to be left to the French. British interests, whether they were shipping or overseas expeditions, were extensive, and they could not rely on others who, with the best will in the world, were apt to lack the resources to do the job. The British were forced to assume the leading part in the antisubmarine war.

The Japanese contribution needs a word of explanation. The British had long been anxious for Japanese assistance. The Japanese had been reluctant to send forces to European waters, although they had, as we have seen, provided considerable assistance in the opening months of the war and later in the search for the German raiders. In mid-April Rear Admiral Kozo Sato arrived at Malta with the Tenth and Eleventh Japanese destroyer flotillas, eight 650-ton Kaba class. Sato flew his flag in the cruiser Akashi, which served as headquarters ship. In August 1917 the Fifteenth Flotilla arrived with four of the new 850-ton Momo class and the armored cruiser Idzumo, which relieved the Akashi. The Japanese were nominally independent, but actually carried out whatever orders they received from the British commander in chief at Malta. The Japanese in fact worked very closely with the British, particularly in escorting troopships. They soon gained an excellent reputation. Their ships were new and well-handled, and the British paid them the ultimate compliment by turning over two of their own H-class destroyers to be renamed and manned by Japanese crews for the duration of the war. This Japanese contribution of fourteen destroyers at a critical moment in the war against submarines has been largely forgotten, but under the circumstances it was far from negligible.

The decisions of the Corfu conference were only recommendations; they naturally had to be accepted by the respective governments. The Admiralty, however, acted fairly quickly, and the Malta-Alexandria convoy was introduced on 22 May with four ships escorted by four trawlers. It proved a success; only two ships were lost between 22 May and 16 July. The French on 18 June formally established a special directorate for the submarine war. The Direction générale de la guerre sous-marine was to a large extent the result of pressure from the French parliament, where there were strong suspicions that the French naval staff had been too tradition-bound and had not paid enough attention to submarine warfare.

Admiral the Honorable Sir Somerset Gough-Calthorpe, second son of the seventh Baron Calthorpe, was appointed British Mediterranean commander in chief. He had formerly commanded the Second Cruiser Squadron and had been second sea lord in 1916. Calthorpe was hardly one of the household names of the war and was deceptively mild mannered. He apparently had a certain amount of difficulty getting his authority accepted by the other commands, but he grew in assurance as time went on. He also possessed good judgment, although he was unfortunately somewhat backward about realizing the value of convoys. At the end of the war he was destined to play a considerable role in negotiating the armistice with the Turks and subsequently became high commissioner in Turkey and the Black Sea. One of his staff officers considered him a man who never sought greatness but had it thrust on him.

The introduction of convoys into the Mediterranean proved difficult. The route structure was complex and the entire Mediterranean was considered a danger area, unlike the situation in the Atlantic where only about 350 miles required special protection for convoys. The British Isles naturally received priority in the allocation of escorts, and the Admiralty added to their own difficulties by insisting that convoys must remain small. There was also the problem of dealing with Allies, notably the Italians. The Italians proved extremely recalcitrant about contributing destroyers and escorts to the common cause, that is, convoys from Gibraltar, and Calthorpe really had no authority over their antisubmarine operations. The Italians insisted they were the only one of the Allies close to the enemy battle fleet, for Pola was only a few hours steaming distance from Venice. They therefore had to retain a significant destroyer force for the protection of Venice and needed their other antisubmarine forces for the protection of Italian traffic in the Tyrrhenian or on the routes to and from Albania and Libya.

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