The USS Zumwalt, the largest destroyer ever built for the US Navy. The 610-foot, 15,000-ton behemoth has begun sea trials before joining the US fleet some time in 2016. Its price tag of $4.4 billion (£2.9 billion) is almost as astounding as its bulk, but US Navy Captain James Kirk, the ship's skipper, said he was "fired up" for the Zumwalt to finally set off for the Atlantic Ocean. So advanced are the Zumwalt's stealth capabilities, that it registers on radar as a small vessel, about the size of a fishing boat. It is about 100ft longer and 20ft wider than the navy's current class of destroyers, and boasts more advanced weaponry. Its computer-guided missile system can hit targets up to 63 miles away, and it may eventually be equipped with a laser weapon or electromagnetic rail gun.
Between October 1916 and January 1917 1,400,000 tons of Allied shipping was lost to German U-boats
On 7 May 1915 the cruise ship Lusitania was torpedoed by a German U-boat – 1,198 people were killed, including 128 Americans
In 1914 SM U-9 (a German U-boat) sank 3 British armed cruisers in under an hour
The Battle of Heligoland Bight (August 1914) was the first naval battle of WW1, and a victory for Britain