ATTP 3-21.50, "Infantry Small-Unit Mountain Operations," provides perspective on Infantry company missions in an operational environment characterized by high-altitudes, rapidly changing climatic conditions, and rugged terrain. It also provides the small-unit leader with guidance on how company-sized units and below can conduct these operations. The mountain environment challenges all warfighting functions. Infantry units are full spectrum organizations, not specifically designed for mountain terrain but are well-suited for mountain operations. Successful units combine the basic doctrine described in FM 3-21.10 and augment with specialized equipment and predeployment training. The tactics and techniques specific to conducting operations in mountain terrain provide added operational capability. This manual focuses on company and below operations in mountain operational terrain levels II and III as described in FM 3-97.6, specifically, where the influence of increasingly steep and rugged terrain dictates the use of dismounted operations. For mountain operations in level I (lower, less rugged valleys and flatter terrain) refer to FM 3-21.10. The concepts discussed in this publication are useful in most mountain environments. This publication applies to the Active Army, the Army National Guard (ARNG)/Army National Guard of the United States (ARNGUS), and the United States Army Reserve (USAR) unless otherwise stated.