The Unforgettable Fire is the fourth studio album by U2. The band wanted a different musical direction following the harder-hitting rock of their 1983 album War, so they employed Brian Eno and Daniel Lanois to produce and assist them experiment with a more ambient and abstract sound. The resulting change in direction was at the time the band's most dramatic. It features atmospheric sounds and lyrics that lead vocalist Bono describes as "sketches". Two songs feature lyrical tributes to Martin Luther King Jr. The title is a reference to "The Unforgettable Fire"—an art exhibit about the atomic bombing of Hiroshima. The band saw the exhibit in November 1983 in Japan while on the War Tour.