They filmed the F4U's in the US, don't know much about it though.
(There were no aircraft above the landing scenes)
But what you see, tanks firing, howitzers firing, .50 cal's firing, explosions throwing sand over the soldiers is actually REAL. It wasn't done with computer graphics, but the old fashioned way. (Actually the cannons fired a real projectile, for the recoil to be real!). The noise on the set was awesome, it was frantic and smoky, you had chaos, cartridges, screaming sergeants, Vehicles stuck in the sand - the works!
I'm a bit disappointed that the colour is somewhat faded (green guys on black sand with blue sea looked really cool), but again that's the artist's power, and I haven't seen the whole thing yet so....
Just got to wait....