On the last day of January 2005, Steven D. Green, the former Army private accused of raping a 14-year-old Iraqi girl and murdering her family, sat in a Texas jail on alcohol-possession charges, an unemployed 19-year-old high school dropout who had just racked up his third misdemeanor conviction.

Days later, Mr. Green enlisted in a soldier-strapped Army, and was later assigned to a star-crossed unit to serve on an especially murderous patch of earth.

He arrived at the very moment that the Army was increasing by nearly half the rate at which it granted what it calls “moral waivers” to potential recruits. The change opened the ranks to more people like Mr. Green, those with minor criminal records and weak educational backgrounds. In Mr. Green’s case, his problems were emerging by junior high school, say people who knew him then.

Mr. Green’s Army waiver allowed a troubled young man into the heart of a war that bore little resemblance to its original declared purposes, but which continued to need thousands of fresh recruits.