"In the late afternoon, after a day's march, he would dig his foxhole"

A one- or two-man hole that soldiers shelter in to protect themselves from enemy fire. Large foxholes allow soldiers to raise their head and shoot. 

In World War II, soldiers used slit trenches, but these offered less protection. Foxholes were the alternative in Vietnam.

Foxholes are not commonly used any more because technology has enabled better forms of protection.