Other than participating in the Battle of Midway and the Battle of the Eastern Solomons in 1942, where she did not see any significant combat, "Mutsu" spent most of the first year of the Pacific War in training. She returned to Japan in early 1943. That June, one of her aft magazines detonated while she was at anchor, sinking the ship with the loss of 1,121 crew and visitors. The IJN investigation into the cause of her loss concluded that it was the work of a disgruntled crew member. The navy dispersed the survivors in an attempt to conceal the sinking in the interest of morale in Japan. Much of the wreck was scrapped after the war, but some artefacts and relics are on display in Japan, and a small portion of the ship remains where it was sunk.