[Zathras]

They were out of range until the B29 was completed and even then, engine failures were a constant problem.
Capturing Iwo Jima was what made it possible.

[smokingfrog]

correct answer

[zeestephen]

Re: “They were out of range until the B29 was completed and even then, engine failures were a constant problem. Capturing Iwo Jima was what made it possible.”

According to my Dad, who set up one of the first radar units on Iwo Jima on D+2, a landing base for crippled B29s was actually a secondary reason for seizing the island.

The primary reason, according to my Dad, was to provide fighter escorts for B-29s. Fighters, of course, had a much smaller flight range than the B-29s, which took off from more distant islands.

Also, Iwo Jima (specifically Mt. Suribachi), when held by the Japanese, was used as an early warning radar outpost against B-29 bombing attacks on mainland Japan.