The US Navy inflicted few losses on the German Navy - one definite U-boat plus others possibly mined in the huge North Sea barrage laid in part by the US Navy between Scotland and Norway. Also few major ships were lost to enemy action - one armoured cruiser and two destroyers. However the large and still expanding US Navy came to play an important role in the Atlantic and Western European waters, as well as the Mediterranean after the declaration of war in April 1917. Most of the battlefleet stayed in American (advertisement) waters because of the shortage of fuel oil in Britain, but five coal-burning dreadnoughts served with the British Grand Fleet as the 6th Battle Squadron (US Battleship Division 9) tipping the balance of power against the German High Seas Fleet even further in favour of the Allies. They were also present at the surrender of the German Fleet. Other dreadnoughts (Battleship Division 6) were based in Berehaven, Bantry Bay, SW Ireland to counter any break-out by German battlecruisers to attack US troop convoys. Some of the pre-dreadnoughts, armoured cruisers and protected cruisers were employed as convoy escorts, 1917-18 both along the coasts of the Americas and in the Atlantic. All three scout cruisers of the 'Chester' class together with some old gunboats and destroyers spent part of 1917-18 based at Gibraltar on convoy escort duties in the Atlantic approaches. The destroyers were part of the at least 36 United States destroyers that reached European waters in 1917-18, many of them based at Queenstown, Ireland, and St Nazaire and Brest, France. Their main duties were patrol and convoy escort, especially the protection of US troopship convoys. Some of the 'K' class (K.5 right in 1919) submarines were based in the Azores and 'L' class at Berehaven, Bantry Bay, Ireland on anti-U-boat patrols 1917-18. In 1917 the programme of large ship construction was suspended to concentrate on destroyers (including the large 'flush decker' classes, 50 of which ended up in the Royal Navy in 1940), submarine-chasers, submarines, and merchantmen to help replace the tremendous losses due to unrestricted U-boat attacks. Some of the destroyers and especially the sub-chasers ended up in the Mediterranean, patrolling the Otranto Barrage designed to keep German and Austrian U-boats locked up in the Adriatic Sea.
