The west Pacific volcanic island of Iwo Jima is declared secured by the U.S. military after weeks of fiercely fighting its Japanese defenders.

The Americans began applying pressure to the Japanese defense of Iwo Jima in February 1944, when B-24 and B-25 bombers raided the island for 74 days straight. It was the longest pre-invasion bombardment of the war, necessary because of the extent to which the Japanese–21,000 strong–fortified the island, above and below ground, including a network of caves. Underwater demolition teams (“frogmen”) were dispatched by the Americans just before the actual invasion to clear the shores of mines and any other obstacles that could obstruct an invading force. In fact, the Japanese mistook the frogmen for an invasion force and killed 170 of them.

The amphibious landings of Marines began the morning of February 19, 1945, as the secretary of the Navy, James Forrestal, accompanied by journalists, surveyed the scene from a command ship offshore. The Marines made their way onto the island–and seven Japanese battalions opened fire, obliterating them. By that evening, more than 550 Marines were dead and more than 1,800 were wounded.

READ MORE: How US Marines Won the Battle of Iwo Jima

In the face of such fierce counterattack, the Americans reconciled themselves to the fact that Iwo Jima could be taken only one yard at a time. A key position on the island was Mt. Suribachi, the center of the Japanese defense. The 28th Marine Regiment closed in and around the base of the volcanic mountain at the rate of 400 yards per day, employing flamethrowers, grenades, and demolition charges against the Japanese that were hidden in caves and pillboxes (low concrete emplacements for machine-gun nests). Approximately 40 Marines finally began a climb up the volcanic ash mountain, which was smoking from the constant bombardment, and at 10 a.m. on February 23, a half-dozen Marines raised an American flag at its peak, using a pipe as a flag post. Two photographers caught a restaging of the flag raising for posterity, creating one of the most reproduced images of the war. With Mt. Suribachi claimed, one-third of Iwo Jima was under American control.

On March 16, with a U.S. Navy military government established, Iwo Jima was declared secured. When all was done, more than 6,000 Marines died fighting for the island, along with almost all the 21,000 Japanese soldiers trying to defend it.

READ MORE: The US Raised the Iwo Jima Flag, then Occupied the Islands for 23 Years