As Andrew Exum C’00 told a Penn Bookstore crowd June 14, midway through his Penn career, he faced a hard decision. “I was told, ‘You can just muddle through or you can be a leader.’ ” Then part of Penn’s ROTC program, Exum opted for the latter, joining the infantry after graduation and serving as platoon leader in operations Enduring Freedom and Iraqi Freedom.

Now the English and Classics major has written “This Man’s Army: A Soldier’s Story from the Front Lines of the War on Terrorism” (Gotham, 2004), about becoming a full-time soldier. “I come from the Volunteer State,” he said. “You just understand when you get to be a man, you go off and serve your country.”

Exum, 25, endured Ranger School and served as platoon leader of 34 men. On September 11, 2001, when he sat around a TV with soldiers in his platoon and watched planes crash into the World Trade Center, “There was no doubt in any of our minds that this changed everything.” Exum deployed to Kuwait, to beef up security, and to Afghanistan, serving for four years before a knee injury forced his departure.

His reason for writing the book is simple: “I wanted to convey what it’s like from a first-person perspective,” he said. “If you watch the news, soldiers are going from one death-defying experience to another. That’s not the way it is.” In his book, said Exum, he wanted to give a sense of the often-slow pace of being stationed in the desert.

Taking questions after his talk, Exum shared some of his favorite war books (“Catch-22,” “The Thin Red Line”), discussed the difficulty of coming home after combat and heaped praise on his fellow soldiers. “This is our generation’s Cold War,” he said gravely. “This is not something that is going away.”