For six long years the Canadian Navy was one of the principal contenders in what was to be known as the Battle of the Atlantic. Beginning the war with a mere 13 vessels and 3,000 men, the Royal Canadian Navy ended it with 373 fighting ships and over 90,000 men. In the crisis of 1940, when German armies were marching into France, four destroyers of the RCN, were sent to the English Channel where they provided aid in the evacuation of forces, landed military troops, and carried out demolitions. After the fall of France the Canadian destroyers joined the Royal Navy in the struggle to protect the southwestern approaches to Britain where German submarines vigorously pressed their attacks. By July 1940 all ocean shipping had to be re-routed around the north of Ireland and through the Irish Sea.