The three Invincible-class battlecruisers were built for the Royal Navy and entered service in 1908 as the world's first battlecruisers.[1] They were the brainchild of Admiral Sir John ("Jacky") Fisher, the man who had sponsored the construction of the world's first "all-big-gun" warship, HMS Dreadnought. He visualised a new breed of warship, somewhere between the armoured cruiser and battleship; it would have the armament of the latter, but the high speed of the former. This combination would allow it to chase down most ships, while allowing it to run from more powerful designs.

This design philosophy would prove to be most successful when the Invincibles were able to use their speed to run down smaller and weaker ships. The classic example was during World War I at the Battle of the Falkland Islands, where Invincible and Inflexible sank the German armoured cruisers SMS Scharnhorst and SMS Gneisenau; despite numerous hits by the German ships, Inflexible and Invincible incurred very few casualties among their crews. They were least successful when standing in the main line of battle, where they faced enemy capital ships. An example is the loss of Invincible to a magazine explosion during the Battle of Jutland about eighteen months after her success in the Falklands, although this explosion owed more to flaws in British ammunition-handling practices – that exposed numerous cordite charges to a fire in one of her gun turrets – than any flaws in the design of the ship.[2]

After the loss of Invincible, the two surviving ships had an uneventful time for the rest of the war conducting patrols of the North Sea, as the High Seas Fleet was forbidden to risk any more losses. They were put into reserve in early 1919 and sold for scrap in 1921.