The Battle of the Atlantic, which lasted the entire war, was a naval conflict often fought between German submarines and American and British shipping. The Germans deployed U-boats as their primary weapon and used them against British, American, and other allied vessels. The first few years of the campaign saw tremendous victories for the Germans, who were able to sink allied shipping with impunity. When the allies began using convoys, the Germans changed their tactics from sending out individual submarines to cover a certain area to gathering several U-boats together in a “wolf pack” and attacking whole convoys at once.