In his journal entry dated July 25, 2002, Tillman described his fellow soldiers: "They're resentful, ungrateful, lazy, weak and unvirtuous. ... One thing I find myself despising is the sight of all these guns in the hands of children. ... Of course, we all understand the necessity of defense but that does not excuse the fact that a young man I would not trust with my canteen is walking about armed."
Tillman joined the Army at age 25 and found himself utterly frustrated by his surroundings.
Former U.S. Army Ranger Kyle Jones, who served alongside Tillman, told ABC News, "There are 50 guys in one huge room and you live there together for 14 weeks. And probably 80 percent of the guys are from age 18 to 22, and it's just a lot of young testosterone in a confined area. I could definitely see it being a little annoying at times."
Tillman's journals also make clear that the hardest thing for him was being away from his wife.
"As always, Marie is on my mind," he wrote in a journal entry dated July 20, 2002. "I have been unable to speak with her ... since we've been here, and I miss the sound of her voice."
Krakauer, who called their relationship very special, said, "She was the love of his life, without a doubt."
In addition to his journal entries about his wife, Tillman sent letters to her regularly and worried about the toll his absence was taking on her.
On their first wedding anniversary, May 4, 2003, Tillman wrote from Afghanistan: "Happy anniversary my love!!! A year ago today Marie made me the luckiest man alive and what have I done in return? Schemed up the most absurd way to drastically s***-can our, until recently, perfect existence. Here I sit in a tent, at Baghdad International Airport, surrounded by kids, half the earth away from where I belong on our anniversary."
But once Tillman joined the Rangers, a tight-knit group of elite infantrymen, he knew he made the right choice.
Former Ranger Jones said, "It's a place where you make lasting brotherhoods. It's like having a group of 15 to 20 brothers. It's different from the regular army. It's guys who want to be there. It's guys who want to do their jobs."
Tillman's personality caught many of his fellow Rangers by surprise.
"He is a very intimidating-looking guy but then once you start to talk to him you're like this guy's nothing what he should be like," Jones recalled. "It just throws you completely off because you look at him and you expect one thing and then you talk to him and you're just like this is one of the coolest guys I've met."
Former U.S. Army Ranger Will Aker, who also fought alongside Tillman, said Tillman did not fit the stereotype of the physical football player turned Army Ranger.
"I think what most people don't know is that there's a lot of intellectual people in the Ranger regiment and Pat was, you know, at the top class of that with his approach to everything," Aker said.
Of his first-time meeting with Tillman, former U.S. Army Ranger Josey Boatright said, "I was going up the stairs and he stopped me and he shook my hand. And he said, 'My name's Pat Tillman. Nice to meet you. Welcome to the 2nd Battalion.' He was the first nice guy I met."
When Tillman joined the Army, he expected his first mission would be in Afghanistan to hunt for the man behind the 9/11 attacks, Osama bin Laden. But the United States invaded Iraq shortly after Tillman completed Ranger school and, in 2003, he deployed there instead.