" Serving officers dare not criticize diversity for fear it will kill their careers. Only after he retired did Army Green Beret Major Andy Messing say that Special Forces units should be homogeneous because this promotes cohesion. He said differences of race or religion add to the tensions of a grinding training regimen and perilous combat missions.
A recent book-length study of cohesion in Civil War units found that soldiers were less likely to desert if they were fighting alongside men who resembled them in ethnicity, religion, and occupation, and who came from the same part of the country. Authors Dora Costa and Matthew Kahn concluded that men were most likely to risk their lives for men who were most like themselves. They also found that Union veterans’ health was worse in old age if they had seen a lot of combat but were surprised to discover that this effect disappeared for soldiers who had fought in very homogeneous units. Fighting alongside close comrades immunized them against battle trauma. "

― Jared Taylor , White Identity: Racial Consciousness in the 21st Century