If former Nebraska Sen. Chuck Hagel is nominated to be the next secretary of defense, it is unlikely that he will have a smooth ride to confirmation.

Leading the Pentagon would mean overcoming an already vocal opposition from pro-Israel groups and others who object to his stance on Iran and Hamas. One group began running ads on Washington-area television stations on Thursday, even though the Obama administration has not offered his name for consideration.

Should he be nominated to replace Leon Panetta, he would bring to the Pentagon a distinct bias against armed conflict forged during the Vietnam War.

Badly burned after his armored personnel carrier hit a land mine in Vietnam, Hagel sat in a medical evacuation helicopter thinking of the horrors he had experienced during his time in combat.

"If I ever get out, if I ever can influence anything, I will do all I can to prevent war," Hagel would later tell his biographer, Charlyne Berens.

The moment was seminal for the young soldier who volunteered to join the Army and ended up serving a yearlong tour in 1968 during the Tet Offensive, considered the most violent period in that war.

Hagel served side by side with his younger brother because of a clerical error. He earned two Purple Hearts, one of which was for saving his brother's life. The second Purple Heart was for shrapnel he took in the chest while on patrol with his brother by his side; his brother saved his life by patching up his wound.

Hagel's time in Vietnam forged his thoughts about combat for the rest of his life, earning him a reputation on Capitol Hill as a senator with an independent streak that meant he was sometimes at odds with his Republican colleagues.

"Not that I'm a pacifist -- I'm a hard-edged realist, I understand the world as it is -- but war is a terrible thing. There's no glory, only suffering," he is quoted as saying in his 2006 biography, "Moving Forward."

Hagel used his Vietnam experience when he criticized the Iraq war early on, including the surge, the plan to put more troops into that country, calling it, "the most dangerous foreign policy blunder in this country since Vietnam, if it's carried out."