Which manual is known as the keystone manual for SF doctrine?

The keystone manual for Special Forces doctrine is FM 3-18. This manual specifically addresses the unique role and operational doctrine of the Special Forces, covering the full spectrum of Special Operations, including unconventional warfare, foreign internal defense, and direct action missions. It serves as a foundational text for understanding the principles, tactics, and techniques essential for Special Forces personnel.

This manual is comprehensive and focuses on the requirements, responsibilities, and operational capabilities of Special Forces units, making it an invaluable resource for both planning and executing special operations missions. Its designation as the keystone manual indicates its critical importance in guiding the training and operational effectiveness of Special Forces soldiers.

In contrast, the other manuals listed cover broader aspects of tactical doctrine or different operational contexts that are not as specific to the unique functions and methodologies employed by Special Forces.