i didn't share it. >> reporter: nathan schmidt was keeping his sorrow inside when, in 2019, a friend d him on a climbing trip. schmidt wasn't a mountaineer. he's afraid of heights. to him, the idea sounded so difficult and frightening, it might just have the force to break his grief. >> yeah. you know, i spent the naval academy preparing myself for war, and nothing can prepare yourself for war. >> reporter: in 2004, schmidt was a 24-year-old first lieutenant, who dreamed of leading marines. he landed in fallujah on the eve of the bloodiest battle of the entire iraq war. >> two weeks after arriving at camp fallujah, i lost my teacher, who was a mentor of mine at the naval academy. >> killed? >> yeah. the rocket struck the office. i was the second one in the room, and it was the first time i'd ever seen anyone die in such a way. and it was my teacher. and that established a crack in me that had to be healed in another way that took years and years to heal. the problem was that was the first of many cracks. i lost one of our marines that was in my unit a month later. i then had my friend