FM 31-21 Guerrilla Warfare and Special Forces Operations: [Annotated] The U.S. Army Field Manual on Unconventional Warfare

by U.S. Department of the Army, Department of the Army

Originally published in 1961, FM 31-21: Guerrilla Warfare and Special Forces Operations is a seminal U.S. Army Field Manual that outlines the principles, tactics, and strategic objectives of unconventional warfare. This historically significant manual explores how small, agile forces can leverage local support and asymmetric tactics to counteract larger conventional military powers. With detailed instruction on organization, intelligence, psychological operations, sabotage, and survival, this field manual remains a cornerstone for understanding the evolution of modern Special Forces doctrine.

Whether you're a military historian, strategy enthusiast, survivalist, or author of military fiction, this manual offers unparalleled insight into guerrilla warfare philosophy and special forces methodology during the Cold War era. This reprint preserves the original formatting, ensuring an authentic look into the doctrines that shaped generations of special operations thinking.

Kindle Edition

Published May 26, 2025

About the author

The Department of the Army (DA) is one of the three military departments within the Department of Defense of the United States of America. The Department of the Army is the Federal Government agency within which the United States Army is organized, and it is led by the Secretary of the Army who has statutory authority 10 U.S.C. § 3013 to conduct its affairs and to prescribe regulations for its government, subject to the limits of the law, and the directions of the Secretary of Defense and the President.

The Secretary of the Army is a civilian official appointed by the President and confirmed by the Senate. The highest-ranking military officer in the department is the Chief of Staff of the Army, who is also a member of the Joint Chiefs of Staff. Other senior officials of the Department are the Under Secretary of the Army (principal deputy to the Secretary) and the Vice Chief of Staff of the Army (principal deputy to the Chief of Staff.)

The Department of War was originally formed in 1789 as an Executive Department of the United States, and was renamed by the National Security Act of 1947 to the Department of the Army on September 18, 1947. By amendments to the National Security Act of 1947 in 1949, the Department of the Army was transformed to its present-day status.

Reviews

[Eric Johnson · Rating 5 out of 5]

As Army FMs go this is an informative one, to say the least. The book is in itself in the boring vernacular of the manuals that the Army puts out. It takes no sides, and focuses on the manual content that it's supposed to. Some of this I had picked up elsewhere, so I skipped a few portions of the book, since it wasn't relevant to me needing just plain information. The interesting note is that it was taken from the original manual written years ago. More or less, it's a rehashing of the old but stil is relevant to doctrine today.