On a stage crowded with war heroes, Mitt Romney recently praised the sacrifice "of the great men and women of every generation who serve in our armed services."

It is a sacrifice the Republican presidential candidate did not make.

Though an early supporter of the Vietnam War, Romney avoided military service at the height of the fighting after high school by seeking and receiving four draft deferments, according to Selective Service records. They included college deferments and a 31-month stretch as a "minister of religion" in France, a classification for Mormon missionaries that the church at the time feared was being overused. The country was cutting troop levels by the time he became eligible for the draft, and his lottery number was not called.

President Barack Obama, Romney's opponent in this year's campaign, did not serve in the military either. The Democrat, 50, was a child during the Vietnam conflict and did not enlist when he was older.

But because Romney, now 65, was of draft age during Vietnam, his military background _ or, rather, his lack of one _ is facing new scrutiny as he courts veterans and makes his case to the nation to be commander in chief. He's also intensified his criticism lately of Obama's plans to scale back the nation's military commitments abroad, suggesting that Romney would pursue an aggressive foreign policy as president that could involve U.S. troops.

A look at Romney's relationship with Vietnam offers a window into a 1960s world that allowed him to avoid combat as fighting peaked. His story also demonstrates his commitment to the Mormon Church, which he rarely discusses publicly but which helped shape his life.

Romney's recollection of his Vietnam-era decisions has evolved in the decades since, particularly as his presidential ambitions became clear.

He said in 2007 _ his first White House bid under way _ that he had "longed in many respects to actually be in Vietnam." But his actions, Selective Service records and previous statements show little interest in joining a conflict that ultimately claimed more than 58,000 American lives.

Still, he repeatedly cites his commitment to public service and the nation's military while campaigning for president.

"Greatness in a people, I believe, is measured by the extent to which they will give themselves to something bigger than themselves," Romney said in San Diego last week to a Memorial Day crowd of thousands, flush with military veterans of all ages.

He did not address his own Vietnam history that day. And his campaign has refused to comment publicly on the subject over the past week.

Political rivals, military veterans among them, suggest that Romney's own decision not to serve in the military is in conflict with his pro-military rhetoric.

"He didn't have the courage to go. He didn't feel it was important enough to him to serve his country at a time of war," said Jon Soltz, who served two Army tours in Iraq and is the chairman of the left-leaning veterans group VoteVets.org.

Critics note that the candidate is among three generations of Romneys _ including his father, former Michigan Gov. George Romney, and five sons _ who were of military age during armed conflicts but did not serve.

As a presidential candidate in 2007, Romney told The Boston Globe he was frustrated, as a Mormon missionary, not to be fighting alongside his countrymen.

"I was supportive of my country," Romney said. "I longed in many respects to actually be in Vietnam and be representing our country there, and in some ways it was frustrating not to feel like I was there as part of the troops that were fighting in Vietnam."

Indeed, Romney strongly supported the war at first. As a freshman at Stanford University, he protested anti-war activists. In one photo, he's shown in a small crowd of students, smiling broadly, wearing a sport jacket and holding up a sign that says, "Speak Out, Don't Sit In."

But the frustration he recalled in 2007 does not match a sentiment he shared as a Massachusetts Senate candidate in 1994, when he told The Boston Herald, "I was not planning on signing up for the military."

"It was not my desire to go off and serve in Vietnam, but nor did I take any actions to remove myself from the pool of young men who were eligible for the draft," Romney told the newspaper.

But that's exactly what Romney did, according Selective Service records. He received his first deferment for "activity in study" in October 1965 while at Stanford.

As Soltz notes, the younger Romney was under no obligation to seek a college-related deferment.

"Vietnam was a war that the poor and the people who couldn't afford to go to college had to go to," Soltz said.

After his first year at Stanford, Romney qualified for 4-D deferment status as "a minister of religion or divinity student." It was a status he would hold from July 1966 until February 1969, a period he largely spent in France working as a Mormon missionary.

He was granted the deferment even as some young Mormon men elsewhere were denied that same status, which became increasingly controversial in the late 1960s. The Mormon church, a strong supporter of American involvement in Vietnam, ultimately limited the number of church missionaries allowed to defer their military service using the religious exemption.

But as fighting in Vietnam raged, Romney spent two and a half years trying to win Mormon converts in France. About that same time, Romney's father would famously speak out against Vietnam, declaring that he had been "brainwashed" by military officials into supporting the conflict.

Young Romney's comments indicated his support had waned, too.

"If it wasn't a political blunder to move into Vietnam, I don't know what is," a 23-year-old Romney would tell The Boston Globe in 1970 during the fifth year of his deferment.

His 31-month religious deferment expired in early 1969. And Romney received an academic studies deferment for much of the next two years. He became available for military service at the end of 1970 when his deferments ran out and he could have been drafted. But by that time, America was beginning to slice its troop levels, and Romney's relatively high lottery number _ 300 out of 365 _ was not called.

Romney's past may not be enough to hurt his popularity in this year's election among veterans, who typically lean Republican.

A Gallup survey released last week found that veterans prefer Romney over Obama by 58 percent to 34 percent. That voting bloc, consisting mostly of older men, makes up 13 percent of the adult population. Obama won the presidency four years ago while losing veterans by 10 points to Sen. John McCain, a former Navy pilot.

Still, some veterans say Romney's reluctance to serve irks them.

"I volunteered for the draft. Romney could have, too. Simple as that," said Wade Lieseke, of Nevada, who served as a helicopter gunner in Vietnam from 1969 to 1970.

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Associated Press Deputy Director of Polling Jennifer Agiesta contributed to this report.