There are many great answers here. In 1910 British Admiral Percy Scott, one of the most forward-thinking naval leaders in British history, wrote a paper saying that the battleship was obsolete and that the submarine was the weapon of the future. H... read more
Nevertheless, the German U-boat campaign was extremely effective and in WW1 the Germans sank over 5000 Allied warships and 13 million tons of shipping with only 358 U-boats compared to sinking about 2800 ships and 14 million tons in World War 2 using about 1200 U-boats. read more
Modern nuclear subs are about as far removed from U-boats as you can get, being capable of continuous running, the nuclear fuel lasting approx 15–20 years, with the only limitation on length of patrol being how much food it can carry. read more
There were a few actions the Allies did to counter the threat of German submarines in World War I and in World War II. In World War I, we told the Germans that if they continued to sink our ships, which violated our rights as a neutral nation, that we would go to war against Germany. read more