Field Manual 3-21

Field Manual 3-21 is a doctrinal publication produced by the United States Department of the Army that codifies infantry tactics, techniques, and procedures for the United States Army and allied forces. It serves as a reference for leaders, soldiers, and trainers from platoon to brigade levels and interfaces with allied doctrines from North Atlantic Treaty Organization, British Army, Australian Army, Canadian Army, and French Army. The manual connects to operational concepts developed during conflicts such as the World War II, Korean War, Vietnam War, Gulf War, and War in Afghanistan (2001–2021).

Background and Purpose

Field Manual 3-21 was developed to standardize infantry doctrine across formations including infantry, mechanized infantry, and air assault units, drawing on lessons from the Normandy landings, Battle of Verdun, Battle of Gettysburg, Tet Offensive, and the First Battle of Fallujah. Its purpose aligns with directives from the Department of Defense, guidance from the Joint Chiefs of Staff, and interoperability goals with partners like NATO, Coalition forces, United Nations, ISAF, and Operation Iraqi Freedom components. The manual synthesizes concepts from seminal works by leaders and theorists such as Carl von Clausewitz, Sun Tzu, Giulio Douhet, Basil Liddell Hart, and practitioners like George S. Patton, Dwight D. Eisenhower, Omar Bradley, and Colin Powell who influenced doctrine through campaigns including the Invasion of Normandy, Operation Overlord, and Operation Desert Storm.

Organization and Content Overview

The manual is organized into sections covering small-unit tactics, weapons employment, reconnaissance, communications, combined arms coordination, and sustainment, referencing historical engagements like the Battle of Britain, Battle of Midway, Siege of Stalingrad, and Operation Market Garden to illustrate principles. It integrates technical details on systems such as the M4 carbine, M16 rifle, M249 SAW, M240 machine gun, Javelin (missile), TOW missile, and platforms like the M1 Abrams, Bradley Fighting Vehicle, UH-60 Black Hawk, CH-47 Chinook, and rotary-wing doctrine influenced by Billy Mitchell. Communications and command sections reference organizations like the Signal Corps, Military Police Corps, Ordnance Corps, and institutions including the United States Military Academy, United States Army War College, and National Defense University to align doctrine with leader development.

Training and Doctrine Applications

FM 3-21 informs institutional training at centers such as the United States Army Training and Doctrine Command, Fort Benning, Fort Bragg, Fort Campbell, Fort Liberty, and the Joint Readiness Training Center. It shapes curricula for courses at the Infantry School, Airborne School, Ranger School, Sapper Leader Course, and developmental programs influenced by historical case studies from Operation Market Garden, Battle of Mogadishu (1993), Siege of Khe Sanh, and Operation Anaconda. The manual coordinates with allied doctrine from the British Army Training Unit Suffield, Canadian Forces Land Force Command, NATO Allied Command Operations, and multinational exercises such as Exercise Bright Star, RIMPAC, and Operation Atlantic Resolve to ensure interoperability in combined arms maneuvers, urban operations, and counterinsurgency campaigns like Operation Enduring Freedom.

Historical Development and Revisions

Revisions to FM 3-21 reflect doctrinal shifts after major conflicts: post‑World War II reforms tied to the Guerre froide, adaptations after the Korean War and Vietnam War, mechanization in the Cold War era, and networked warfare learnings from Operation Iraqi Freedom and War in Afghanistan (2001–2021). Contributors include analysts from the Rand Corporation, Center for Strategic and International Studies, and the Institute for Defense Analyses, and reflect directives from secretaries and chiefs such as Robert McNamara, Caspar Weinberger, Donald Rumsfeld, and James Mattis. Doctrinal evolution incorporated counterinsurgency concepts influenced by theorists and operators engaged in campaigns like Malayan Emergency, Northern Ireland conflict, and the Soviet–Afghan War.

Implementation and Use in Operations

Commanders and staff employ FM 3-21 during planning and execution of operations from company to division levels in contexts including conventional offensive and defensive actions, stability operations, peacekeeping under United Nations Peacekeeping, and security cooperation missions with partners like Japan Self-Defense Forces, South Korea Armed Forces, German Army, and Italian Army. The manual supports integration with joint assets such as United States Air Force, United States Navy, United States Marine Corps, and coalition logistics from NATO Support and Procurement Agency. Case studies in the manual reference operations including Operation Torch, Battle of Fallujah (2004), Operation Allied Force, and Operation Neptune Spear to teach synchronization of fires, maneuver, reconnaissance, and sustainment across complex battlespaces.

Category:United States Army doctrine