This United States Army publication, Field Manual FM 3-34 Engineer Operations December 2020, contains the capstone doctrinal guidance for U.S. Army engineers. FM 3-34 demonstrates how engineers contribute to decisive action and provides a common framework and language for engineer support to operations. It also constitutes the doctrinal foundation for developing other fundamentals and tactics, techniques, and procedures detailed in subordinate engineer publications. This manual is the integrating publication that nests engineer doctrine with Army capstone doctrine and joint doctrine. It focuses on synchronizing and coordinating the diverse range of capabilities in the Engineer Regiment to support the Army and its mission successfully. FM 3-34 provides operational guidance for engineer commanders and trainers at all echelons and forms the foundation for the United States Army Engineer School (USAES) curricula. The principal audience for this manual is engineer leaders, commanders, noncommissioned officers, and staff officers, but all Army leaders benefit from reading it. Trainers, educators, and combat developers throughout the Army also benefit from using this manual. FM 3-34 applies to the Active Army, Army National Guard/Army National Guard of the United States and United States Army Reserve unless otherwise stated.