Battleship
Many battleships were used in the First World War. However, battleships were so important and expensive that neither side wanted to take a chance of losing a battle with them. There were several battles with battleships. The biggest one was the Battle of Jutland which involved dozens of battleships and hundreds of smaller ships. But none of the battles made much difference. Submarines made a bigger difference to the war, even though less people had expected them to. At the end of the War, Germany was made to hand over all their battleships to Britain. However, the German navy sank ("scuttled") their own battleships rather than give them to the British. In 1922, most countries which had big navies signed a treaty called the Washington Naval Treaty which meant no-one would build new battleships for at least 10 years.