Berets of the United States Army
U.S. Army Special Forces wear the green beret because of their link to the British Commandos of World War II. The first Ranger unit, commonly known as Darby's Rangers, was formed in Northern Ireland during the summer of 1942. On completion of training at the Commando Training Depot at Achnacarry Castle in Scotland, those Rangers had the right to wear the British Commando green beret, but it was not part of the regulation uniform at the time and was disallowed by the U.S. Army. 
The 10th Special Forces Group (Airborne) had many veterans of World War II and Korea in its ranks when it was formed in 1952. Members of the 10th SFG began to unofficially wear a variety of berets while training, some favoring the red or maroon airborne beret, the black beret, or the green commando beret. In 1953, a beret whose design was based on that of the Canadian Army pattern, and which was rifle-green in color, was chosen for wear by Special Forces units.
Michael John Hurdzan
A senior writer and equipment editor for WorldGolf.com (powered by Golf Channel), Kiel Christianson wrote that "[Hurdzan] served for 23 years as commander of Green Beret[s] and Psychological Operations units in the U.S. Army Reserve, specializing in survivalist tactics." Howard Richman wrote in the December 2012 issue of the "Golf Course Management (GCM) Magazine" that "Nearly 40 years ago — before Hurdzan emerged among the world’s most notable and decorated golf course architects — he traveled the globe to protect America's interests. As a commander for the U.S. Army Special Forces, also known as the Green Berets, Hurdzan prepared his unit in case it needed to be called to action in theaters of war or conflict, such as Vietnam. Part of their war games training included missions in places such as Germany". Richman also wrote that an architecture editor for Golf Digest, "[Ron] Whitten is convinced that Hurdzan, who chose not to pursue the rank of general, earned his stripes. Twice Hurdzan's orders to join the fighting in Vietnam were canceled (he was supposed to go there to spray jungles after he was schooled in chemical, biological and radiological warfare). Not seeing combat left him unfulfilled. "I wanted to be a real live warrior, a cutter and a shooter, not some technical geek," Hurdzan says. If he had fought for his country, Whitten imagines Hurdzan would have been outstanding." Richman concluded that, "convinced he has lived a charmed life, [Hurdzan is] thankful now that Vietnam wasn't in the cards for him so long ago."