This manual, "Opposing Force Operations (FM 7-100.1)," is one of a series that describes a contemporary Opposing Force (OPFOR) for training U.S. Army commanders, staffs, and units. Together, these manuals outline an OPFOR than can cover the entire spectrum of military and paramilitary capabilities against which the Army must train to ensure success in any future conflict. This OPFOR reflects the characteristics of military and paramilitary forces that may be present in the contemporary operational environment (COE). Like those real-world threats, the OPFOR will continue to present new and different challenges for U.S. forces. The COE is constantly changing, and it is important for U.S. Army training environments to keep pace with real-world developments. Trainers should use appropriate parts of the OPFOR manuals to fill information gaps in a manner consistent with what they do know about a specific threat.