Originally formed at the turn of the nineteenth century to protect America’s strategic interests in the Caribbean, the 65th Infantry was composed of locally recruited Puerto Rican soldiers led primarily by non-Hispanic “continental” officers. Although in existence for almost fifty years, the 65th had not experienced intense combat until it was committed to the Korean peninsula in the initial months of the war. There, despite its lack of previous wartime service, the regiment did extremely well from September 1950 to August 1951, establishing a solid reputation as a dependable infantry unit and a mainstay of the heavily embattled 3d Infantry Division. After that period, however, its performance began to suffer as experienced cadre rotated out of the regiment and were replaced by new leaders and soldiers who lacked the skills and special cohesive bonds displayed by their predecessors. The net result was a highly publicized series of incidents and disciplinary actions that have never been adequately explained or understood. This study reviews the performance of the 65th Infantry throughout the war, providing insights not only into the regiment’s unique problems but also into the status of the U.S. Army’s combat forces during one of the most trying periods in its history. Its findings underscore the critical impact of personnel-rotation policies, ethnic and organizational prejudices, and the work of small-unit leaders on combat readiness and battlefield success. They also illustrate the critical role of senior leaders in analyzing problems in these areas in a timely fashion and instituting effective reforms. For the 65th, a catastrophic shortage of trained NCOs, unaddressed language problems, and inept command leadership temporarily undermined its combat effectiveness. Making matters worse, senior commanders reacted in a heavy-handed manner with little analysis of what was really going on. In the end, it was the martial traditions of the 65th’s Hispanic soldiers and a h