World War II: Limpet mines placed by Italian divers heavily damage HMS Valiant and HMS Queen Elizabeth in Alexandria harbour.

A limpet mine is a type of naval mine attached to a target by magnets. It is so named because of its superficial similarity to the shape of the limpet, a type of sea snail that clings tightly to rocks or other hard surfaces.

The Italian Navy is one of the four branches of Italian Armed Forces and was formed in 1946 from what remained of the Regia Marina after World War II. As of August 2014, the Italian Navy had a strength of 30,923 active personnel, with approximately 184 vessels in service, including minor auxiliary vessels. It is considered a multiregional and a blue-water navy.

HMS Valiant was one of five Queen Elizabeth-class battleships built for the Royal Navy during the early 1910s. She was built at Devonport Royal Dockyard between January 1914 and November 1914, and entered service shortly after the outbreak of the First World War. She participated in the Battle of Jutland during the First World War as part of the Grand Fleet. Other than that battle, and the inconclusive Action of 19 August, her service during the war generally consisted of routine patrols and training in the North Sea.

HMS Queen Elizabeth was the lead ship of her class of five dreadnought battleships built for the Royal Navy in the early 1910s, and was often used as a flagship. She served in the First World War as part of the Grand Fleet, and participated in the inconclusive action of 19 August 1916. Her service during the war generally consisted of routine patrols and training in the North Sea. She and the other super-dreadnought battleships were the first of their type to be powered by oil instead of coal. Queen Elizabeth later served in several theatres during the Second World War, and was scrapped in 1948.