During the first three decades of the present century, the Marine Corps served as the striking arm of the United States policy of Caribbean intervention. In 1916, Marines landed in the Dominican Republic to protect foreign lives and property and to provide the "muscle" for a United States military government which was trying to bring stability to the troubled island republic. While there, Marines performed a variety of functions not normally assigned to an occupying military force, and they gained experience which helped to provide a pool of combat-trained leaders for future conflicts. This study is based on primary sources contained in the archives and holdings of the History and Museums Division, Headquarters, Marine Corps, the Federal Records Center, Suitland, Maryland, and the National Archives. In these sources, the record of the Dominican occupation is set forth, often in painstaking details. From research in these records, several themes, common to similar Marine campaigns in neighboring Haiti and in Nicaragua, became apparent. The first of these is the paramount role played by the Marine Corps in establishing and training a native constabulary capable of maintaining order after the Marines withdrew. Secondly, effective tactics for the conduct of counter-insurgency operations emerged from these interventions: for example, the coordinated use of air and ground forces began during these campaigns. The third important theme was the gradual development among Marines stationed in these Latin republics of the concept of what would be called in Vietnam "civic action" -- efforts by the occupying troops to "win the hearts and minds" of the population.