HMS Renown (1916) in the context of "Renown-class battlecruiser"

The Norwegian campaign (8 April – 10 June 1940) involved the attempt by Allied forces to defend northern Norway coupled with the Norwegian military's resistance to the country's invasion by Nazi Germany in World War II.

Planned as Operation Wilfred and Plan R 4, while the German attack was feared but had not yet happened, the battlecruiser HMS Renown set out from Scapa Flow for Vestfjorden with twelve destroyers on 4 April. The Royal Navy and the Kriegsmarine met at the first and second naval battles of Narvik on 10 and 13 April, and British forces conducted the Åndalsnes landings on 13 April. The main strategic reason for Germany to invade Norway was to seize the port of Narvik and guarantee the delivery of iron ore needed for German steel production.

The Singapore strategy was a naval defence policy of the United Kingdom that evolved in a series of war plans from 1919 to 1941. It aimed to deter aggression by Japan by providing a base for a fleet of the Royal Navy in the Far East, able to intercept and defeat a Japanese force heading south towards India or Australia. To be effective it required a well-equipped base. Singapore, at the eastern end of the Strait of Malacca, was chosen in 1919 as the location of this base; work continued on this naval base and its defences over the next two decades.

The planners envisaged that a war with Japan would have three phases: while the garrison of Singapore defended the fortress, the fleet would make its way from home waters to Singapore, sally to relieve or recapture Hong Kong, and blockade the Japanese home islands to force Japan to accept terms. The idea of invading Japan was rejected as impractical, but British planners did not expect that the Japanese would willingly fight a decisive naval battle against the odds. Aware of the impact of a blockade on an island nation at the heart of a maritime empire, they felt that economic pressure would suffice.

HMS Repulse was one of two Renown-class battlecruisers built for the Royal Navy during the First World War. Originally laid down as an improved version of the Revenge-class battleship, her construction was suspended on the outbreak of war because she would not be ready in time. Admiral Lord Fisher, upon becoming First Sea Lord, gained approval for her to resume construction as a battlecruiser that could be built and enter service quickly. The Director of Naval Construction (DNC), Eustace Tennyson-d'Eyncourt, quickly produced an entirely new design to meet Admiral Lord Fisher's requirements and the builders agreed to deliver the ship in 15 months. They did not quite meet that ambitious goal, but the ship was delivered a few months after the Battle of Jutland in 1916. Repulse and her sister ship Renown were the world's fastest capital ships upon completion.

Repulse participated in the Second Battle of Heligoland Bight in 1917, the only combat she saw during the war. She was reconstructed twice between the wars; a reconstruction in the 1920s increased her armour protection and made lesser improvements, while another in the 1930s was much more thorough. Repulse accompanied the battlecruiser Hood during the Cruise of the Special Service Squadron on a round-the-world cruise in 1923 to 1924 and protected international shipping during the Spanish Civil War in 1936 to 1939.