<P> World War I was the first conflict in which submarines were a serious weapon of war . In the years shortly before the war, the relatively sophisticated propulsion system of diesel power while surfaced and battery power while submerged was introduced . </P> <P> The United Kingdom relied heavily on imports to feed its population and supply its war industry, and the German Navy hoped to blockade and starve Britain using U-boats to attack merchant ships in unrestricted submarine warfare . This struggle between German submarines and British counter measures became known as the "First Battle of the Atlantic". As German submarines became more numerous and effective, the British sought ways to protect their merchant ships . "Q - ships", attack vessels disguised as civilian ships, were one early strategy . </P> <P> Consolidating merchant ships into convoys protected by one or more armed navy vessels was adopted later in the war . There was initially a great deal of debate about this approach, out of fear that it would provide German U-boats with a wealth of convenient targets . Thanks to the development of active and passive sonar devices, coupled with increasingly deadly anti-submarine weapons, the convoy system reduced British losses to U-boats to a small fraction of their former level . Lieutenant Otto Weddigen remarked of the second submarine attack of the Great War: </P> <Table> <Tr> <Td> "</Td> <Td> How much they feared our submarines and how wide was the agitation caused by good little U-9 is shown by the English reports that a whole flotilla of German submarines had attacked the cruisers and that this flotilla had approached under cover of the flag of Holland . These reports were absolutely untrue . U-9 was the only submarine on deck, and she flew the flag she still flies--the German naval ensign . </Td> <Td>" </Td> </Tr> </Table>

During world war i developments in military technology lead to