The Green Berets primarily train in filipino kali...thats where their entire knife and blade system comes from...Now in terms of grappling they still stick mostly with filipino arts...they emphasize many chokes locks and counter offensive manipulations...although the standard martial arts course for SF is only 6 weeks in length they typically have the ability to take most seasoned blackbelts because of the practicality that they learn...Their techniques are very versitaille in that one move can apply to many situations...the systems they use are also designed to work in the field...when they will be tired and hungry so it doesnt rely on brute strength all the time eventhough id watch out while they are healthy because they are very strong...Im not sure of every system they use but i know some of it is derived from kali, hapkido, krav maga, JKD, and a few other arts specifically developed for the military...there has been much reform in their training the past years in ways of not only physical training, but even some menttal and spiritual work as well.......