Naval power was crucial in World War I, particularly for Britain, which relied on its navy to protect its empire and import food and supplies.

The British Royal Navy established a naval blockade of Germany to cut off its access to vital resources.

The main surface fleets of Britain and Germany met only once in a major battle, the Battle of Jutland in 1916, which was largely inconclusive.

Germany's most effective naval weapon was the U-boat (submarine).

In response to the British blockade, Germany declared a policy of 'unrestricted submarine warfare,' sinking any ship approaching Britain.

The sinking of the British passenger liner Lusitania in 1915 by a U-boat killed over 1,200 people, including 128 Americans, and caused international outrage.

Germany briefly halted the policy but resumed it in 1917, hoping to starve Britain into surrender before the United States could enter the war.

The resumption of unrestricted submarine warfare was a key reason for the U.S. decision to declare war on Germany.

The Allies eventually developed effective countermeasures to the U-boat threat, such as the convoy system.

The naval war played a critical, though often overshadowed, role in the Allied victory.