The Green Beret runs a demanding training program for applicants and trainees can wash out if they dont pass the tests. According to the letter however the program is being altered so that trainees so graduates can complete the training without passing physical tests or land navigation tests.
In fact the nearly twoyear course of Green Beret training has a plan to get reduced in 2020. Check back with Operation Military Kids for the latest updates on new Green Beret training standards. Additionally here is an interesting excerpt from the book The Guerrilla Factory The Making of Special Forces Officers The Green Berets.