Britain and France declared war on Germany after Hitler invaded Poland on a pretext. France fell quickly and Britan was left to face Germany alone. Roosevelt was hamstrung by his isolationist Congress and had to engage in all sorts of trickery to aid the British Island economy, which depended on ocean shipping for its food, supplies and fuel. Its lifeline of shipping was threatened by a very strong German submarine fleet. Britan had to fight the battle under the waves of the Atlantic alone to survive, aided by fifty old American destroyers lent by Roosevelt. After the United States was attacked, it found itself a full participant in the war against the Japanese and Hitler, including the battle of the Atlantic against the German U-boats. In the early part of the war, Britain was on the brink of defeat, but British and American warships and planes depth charged, bombed, and rammed the U-boats until merchant shipping, troopships and tankers could safely cross the Atlantic. The defeat of Germany was in no small measure their defeat under the waves of the Atlantic. This is the story of how, from the darkest days of the war, Britain and American, under the leadership of Churchill and Roosevelt, defeated the U-boats and its commander-in-chief, Grand Admiral Karl Dönitz.
