World War II: A U.S. Navy task force turned away an Imperial Japanese Navy formation at the Battle of Empress Augusta Bay, thus protecting the landings at Cape Torokina.

World War II or the Second World War was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.

The United States Navy (USN) is the maritime service branch of the United States Department of Defense. It is the world's most powerful navy with the largest displacement, at 4.5 million tons in 2021. It has the world's largest aircraft carrier fleet, with eleven in service, one undergoing trials, two new carriers under construction, and six other carriers planned as of 2024. With 336,978 personnel on active duty and 101,583 in the Ready Reserve, the U.S. Navy is the third largest of the United States military service branches in terms of personnel. It has 299 deployable combat vessels and about 4,012 operational aircraft as of 18 July 2023. The U.S. Navy is one of six armed forces of the United States and one of eight uniformed services of the United States.

The Imperial Japanese Navy was the navy of the Empire of Japan from 1868 to 1945, when it was dissolved following Japan's surrender in World War II. The Japan Maritime Self-Defense Force (JMSDF) was formed between 1952 and 1954 after the dissolution of the IJN.

The Battle of Empress Augusta Bay, on 1–2 November 1943 – also known as the Battle of Gazelle Bay, Operation Cherry Blossom, and in Japanese sources as the Sea Battle off Bougainville Island (ブーゲンビル島沖海戦) – was a naval battle fought at night in Empress Augusta Bay near Bougainville Island. The naval battle was a result of Allied landings at Cape Torokina in the first action in the Bougainville campaign of World War II. It may also be considered as part of the Solomons and New Guinea campaigns. The battle was significant as part of a broader Allied strategy—known as Operation Cartwheel—aimed at isolating and surrounding the major Japanese base at Rabaul. The intention was to establish a beachhead on Bougainville, within which an airfield would be built.