Soldiers have always had to endure a variety of nicknames. During World War I, they were called doughboys because crawling through the European mud gave their uniforms a dough-like color. During World War II, they were called G.I.s, short for government issue, classifying the soldier as yet one more commodity in an endless line of government products created to win the war. They were also called sad sacks, after a cartoon character who epitomized their status as victims of the bureaucracy of war.

For the soldiers who served in the Vietnam War, the word grunt was not just a nickname but also a commentary on their status in the hierarchy of war. To be a grunt was to be in the infantry. It meant leaping out of helicopters into landing zones that were sometimes under enemy fire. It meant marching through elephant grass taller than a...