ground-pounder
n.β Β«I went to the school of infantry, also known as S.O.I. They say that S.O.I. graduates (grunts or ground-pounders) have one of the youngest mortality rates of any school in history because thousands of alumni have gone on to die in armed conflict before the age of 25. Β» ββA Few Bad Men” by Gabe Hudson New York Times Nov. 19, 2006. (source: Double-Tongued Dictionary)