“The Sands of Iwo Jima”
I recall interviews with Marines on Iwo. They said the sand was so hot because it was volcanic. You couldn’t dig much of a trench because it got hotter as you went deeper - and pretty soon too hot to get into. But, they would dig a small hole a bit deeper to heat their rations!
And it was deep, loose sand. The two steps up, one step back kind. It almost seemed that they hated the sand more than the enemy in their recollections.
The former Sgt Major I used to work with said the same things about Iwo that you posted. It was hard to dig a fighting hole since the coarse sand would not stick together and stay dug. Ditto on heating up the rations.