Well I'm a lot further now :P Though I saw the nests during the Ocelot duel and felt really clever for using them. I just talked to that Russian guy that told me to backtrack to the warehouse.
Question: Any time I'm approaching a soldier from behind, he magically turns around and sees me (unlike MGS1 and 2). I go slow, and those fuckers keep magically sensing me. I know I'm doing something wrong, because I rarely pull off CQC at all. How I do suck less?