World War II: The Naval Battle of Guadalcanal, the decisive engagement in a series of sea battles between Allied and Japanese forces during the months-long Guadalcanal campaign in the Solomon Islands, began.

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 Naval Battle of Guadalcanal took place from 12 to 15 November 1942 and was the decisive engagement in a series of naval battles between Allied and Imperial Japanese forces during the months-long Guadalcanal campaign in the Solomon Islands during World War II. The action consisted of combined air and sea engagements over four days, most near Guadalcanal and all related to a Japanese effort to reinforce land forces on the island. The only two U.S. Navy admirals to be killed in a surface engagement in the war were lost in this battle.

Naval warfare is combat in and on the sea, the ocean, or any other battlespace involving a major body of water such as a large lake or wide river.

The Allies, formally referred to as the United Nations from 1942, were an international military coalition formed during World War II (1939–1945) to oppose the Axis powers. Its principal members were the "Big Four" – the United Kingdom, United States, Soviet Union, and China.