system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do armies collect their dead soldiers?

I'm just watching "The Pacific" and during the battle scenes, I got to wondering how various armies collected their dead.
gpt
Often, they didn’t in places like iwo jima. Those to-the-last-man island fights were brutal and there was rarely a chance to collect the dead.

Many Japanese remain where they fell, or were collected up by the US forces and buried in mass graves.

Most US soldiers were recovered hours to weeks after a battle, and usually repatriated to the US. 

Historically, armies would sometimes allow groups from either side to move around openly in front of the guns to collect the dead and wounded, but not often since the 1800s.

And places like the Somme, the dead remain in the ground where they died.