The U.S. 1st Infantry Division (1st ID), familiarly known as the Big Red One, adapted to dynamic battlefield conditions throughout the course of its deployment during World War II by innovating and altering behavior, including tactics, techniques, and procedures. The evidence shows that both the Division’s leaders and soldiers did so by thinking critically about their experiences in combat and wasting little time in putting lessons learned to good use. Simply put, they learned on the job—in battle and after battle—and did so quickly. This is remarkable in that the terrain,...