The Battle of Iwo Jima took place in 1945, during WWII, when the US forces landed on and conquered the island with the same name by defeating the Imperial Japanese Army (IJA) army.
The mission was known as the Operation Detachment, and it was regarded as strategically crucial as, after capturing Iwo Jima, the Americans could dominate its four airfields and conduct air attacks against other Japanese islands. It also constituted a necessary and safe stop to land and refuel. These were the justifications provided to respond for the huge number of casualties suffered by the American forces.