That's what I was considering. At least, unlike with the D-Day bombardments, there was no possibility of artillery's hitting "friendlies."
There were a couple of reasons we were “softening up” Iwo:
1. The Japanese had used Iwo as a forward airbase to launch strikes on our bomber bases in the Marianas. We wanted that threat neutralized. That has been the primary focus of the B-24 raids.
2. We don’t want the Japanese using their air bases to send fighters up against B-29s headed for the Home Islands. That’s also part of the focus of the B-29 raids.
3. However, the shore bombardment raids are telltale signs we intend to seize those islands. I’m sure the Japanese know the range of the P51 Mustang, thanks to their German allies, and that American strategic air doctrine prefers the big bombers be escorted by fighters.
They knew we were coming; there was no chance of surprise.
But while the shore bombardment was considered ineffective, was it really? During the pre-invasion bombardment on February 17, USS Pensacola received six hits from shore batteries. At the very least, those batteries had to be suppressed. And even if the bombardment didn’t kill all the Japanese on the island and destroy all their weapons, it didn’t hurt to try.