73 years ago a war photographer snapped the most iconic image of WWII — here's the incredible story of the battle behind the photo

Iwo Jima Joe Rosenthal / AP

The Battle of Iwo Jima holds a special place in the history of the United States.

Remembered for the iconic photo that AP photographer Joe Rosenthal took of US Marines raising the flag over Mount Sriracha, the nearly six week-long battle in 1945 saw over 100,000 US soldiers, sailors, and airmen fight around 21,000 soldiers of the Empire of Japan.

Dubbed Operation Detachment, the objective was to capture the entire island, wipe out its defending garrison, and use its three airfields and infrastructure as a staging ground for attacks on the Japanese mainland. Iwo Jima was also intended to support efforts for the planned invasion of the Japanese mainland itself — Operation Downfall.

American victory was never in any doubt; the US had an overwhelming numerical advantage, complete aerial superiority, and had entirely cut off the island, preventing the chance for retreat or reinforcement.

But the Japanese had prepared for a massive battle on the island. They had evacuated all civilians and burned all the vegetation and brush to eliminate places where the Americans could conceal themselves.

Most importantly, the Japanese had built a massive network of tunnels and bunkers all over the island that enabled them to access any part of the island and wait out long bombardments.

In the end, out of the 21,000-strong Imperial garrison, only 216 were taken prisoner. The rest of the soldiers died in combat or committed suicide — though an estimated 3,000 soldiers refused to surrender and continued to live in the island's massive underground fortifications, conducting raids and guerilla-style attacks.

The last Japanese soldiers to surrender on Iwo Jima did so on January 6, 1949, nearly four full years after the start of the battle.

Though Japanese combat deaths were three times higher than those of the US forces, total American casualties, which include dead and wounded, were higher than those of the Japanese — 6,821 Americans were killed, over 19,000 wounded, one escort carrier sunk, and a number of ships damaged.

Check out some of the photos of the battle here:

Iwo Jima was strategically important, enough so that air and naval bombardments of the island started in June of 1944, almost a year before the battle.

Associated Press

Iwo Jima's location provided Japanese fighters with a base to intercept US aircraft on their way to attack the Japanese mainland, and it was an important station for its Navy. The US decided it had to be taken, and the first operations against Iwo Jima started as early June of 1944.

But the island had been turned into a fortress by Lieutenant General Tadamichi Kuribayashi. By the time the Americans invaded, Japanese soldiers had dug 11 miles of bunkers and tunnels all around the island.

Because they were so deep, the Japanese could wait out any bombardments. One bunker was up to 90 feet deep.

The US barraged Iwo Jima with naval bombardments for three days. Though the explosions did knock out some trenches and caves, the affect was still limited due to the tunnels and bunkers.

US Navy

The commander of the Marine landing force had originally requested 10 days of shelling the island, but the Navy cut it down to three.

Bad weather, combined with the Japanese tunnel and bunker networks limited the damage that the barrages could do. Some American ships were even hit by returning fire from the Japanese.