The raids were increasingly effective but also costly.

The round trip from the Marianas to Japan and back was nearly three thousand miles.

Bombers that were damaged over Japan had nowhere to land.

They ditched in the Pacific and their crews were lost.

Fighter aircraft couldn’t fly that range at all, which meant the B-29s flew without escort.

Iwo Jima, sitting roughly midway between the Marianas and Japan, changed that equation.

A Japanese-held air base on Iwo Jima, it was used to intercept the B-29s and provide early warning to Japan’s defenses.