Does anyone know when Marines first started using the large boards/concrete on the side if Shermies? What is the earliest island it would it be appropriate for?

The earliest version I have seen with wood add on was on Saipan, early M4A2. The classic version with wood, spaced out and concrete fill, seems to start on Iwo, and continues on to Okinawa. Some one borrowed my best book so this is the best I can do.

Thanks Randall, I think that you're right. I do also seem to recall Iwo as being when it started. I just wanted to make sure. It always helps to have a second opinion!