At 10:59 a.m. on Nov. 11, 1918, a German machine gun crew fired a burst of rounds at approaching Americans. One bullet struck 23-year-old Pvt. Henry Gunther in the left temple. He died instantly.

Few weapons have defined the tempo of modern warfare quite like the machine gun. It isn’t a new concept by any means, with the notion of rapid fire volleys being something dating back to the Age of ...