only 30 ocean-going submarines, 20 of 500 tons and 10 of 750 

 tons , 



But if the number of German U-boats was small, so was 

 the number of anti-submarine craft available to the British - 

 only some 165 destroyers, 35 small patrol craft and 20 trawlers 

 fitted with ASDIC devices . Prance had 59 destroyers By com- 

 parison, more than 3,000 vessels, including some 900 destroyers 

 and 170 patrol craft, had been available to the Allies for 

 anti-submarine warfare in 1918 „ 



Despite the shortage of escort vessels, the British 

 profited by their World War I experience and immediately 

 adopted the convoy system. The Germans, however, were able 

 to find numerous vessels sailing independently and merchant 

 ships began to be sunk at a dismaying rate„ 



Shore-based aircraft cf the British Coastal Command 

 shared in the defense against the U-boats „ Though ineffective 

 in attack, they did tend to keep the U-boats submerged. 



In October 1939, Prien, commander of U-47, penetrated 

 Scapa Flow and sank the battleship HMS ROYAL OAK - a disaster 

 to the British which had one fortunate aspect In that it 

 brought home the need of protecting harbors against submarine 

 attack by means of underwater sound equipment 



June 1940, closing month of Period I, was a dark month 

 for the AllieSo Allied shipping losses to U-boats rose to 

 56 ships of 267,000 gross tons. Prance fellj Italy entered the 

 war with more than 100 submarines, of which some 60 were ocean- 

 going. 



As assessment of the events during the ten months of Period 

 I in the U-boat war showed that on the whole the convoy system 

 was effective . Some 2500 ships a month had been convoyed with 

 losses to U-boats of ships in convoy of only 5 per month. 

 Merchant vessels not in convoy were sunk by U-boats at a rate 

 four times as high. 



On the debit side of the Allied ledger, however, ship- 

 ping losses of the allied and neutral nations from all causes 

 amounted to 280,000 gross tons per month of which 223,000 

 gross tons were due to enemy action, 106,000 gross tons being 

 losses to U-boats. 



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