The Mitsubishi G4M is a twin-engine, land-based medium bomber formerly manufactured by the Mitsubishi Aircraft Company, a part of Mitsubishi Heavy Industries, and operated by the Imperial Japanese Navy from 1940 to 1945. Its official designation is Mitsubishi Navy Type 1 attack bomber and was commonly referred to by Japanese Navy pilots as Hamaki due to the cylindrical shape of its fuselage and its tendency to ignite after a hit. The Allied reporting name was "Betty".

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.