Holding black belts in several martial arts, he served as the noncommissioned officer in charge (NCOIC) of Combatives training for the second Ranger Battalion and as the program grew the entire 75th Ranger Regiment, where he was also regimental master trainer for Close Quarters Battle and Marksmanship, the Ranger Training Brigade where he authored FM 3-25.150, and finally for the entire Army. Since retiring from the Army in 2005, Mr. Larsen has, worked as a security contractor around the world to include both Afghanistan and Iraq, helped rewrite the Combatives curriculum for the United States Army John F. Kennedy Special Warfare Center, the US Air Force, the Canadian Special Operations Regiment, and has consulted with both the Royal Marine Commandos as well as the British Army's Infantry on the development of their Combatives programs.
He has twice rewritten the Army Field Manual on hand-to-hand combat, FM 3-25.150 (Combatives), in both 2002 and 2009, edited two books on Survival and evasion for the publisher Lyons Press, and has a book about snipers in Iraq and Afghanistan that he co-authored that will be available in September also from Lyons Press.
Currently He is both a trainer and consultant on Combatives and Combatives training systems, Marksmanship, all aspects of Close Quarters Battle and small unit tactics that he learned over his 27 years of experience as both an operator and a teacher. He has literally revolutionized Combatives training and the culture of the United States Military with training methods and concepts that are becoming the standard around the world.
Source : http://www.moderncombatives.org