American troops have been fighting and dying in Iraq and Afghanistan for more than four years, but just one soldier from those wars has received the Medal of Honor, the nation's highest honor for bravery.

The lack of such medals — by comparison, two were awarded for fighting in Somalia — reflects today's unconventional warfare and the superior weaponry of U.S. forces, military experts say. It's not that today's troops lack valor, but they lack opportunities to display it in the extraordinary way that would merit the Medal of Honor.

"The situations today are less likely to warrant the Medal of Honor than in past conflicts," says Nicholas Kehoe, president of the Congressional Medal of Honor Foundation. "That doesn't mean our troops aren't acting courageously or even heroically."

Kehoe, a retired Air Force lieutenant general and not a recipient of the medal, says the dominance of air power and the use of such tools as night-vision goggles give U.S. forces huge advantages. "We don't charge up hills with machine-gun nests anymore," he says.

Insurgents' tactics in Iraq — remotely detonated explosives and suicide bombers — also mean U.S. troops often don't have the opportunity to respond heroically.

"We don't have full frontal battles, like the Battle of the Bulge," says David Burrelli, a specialist in national defense for the Congressional Research Service.

Charles Moskos, a military sociologist at Northwestern University, points out that patrolling where insurgents plant bombs takes courage. However, it doesn't require the out-of-the-ordinary valor required for the Medal of Honor, he says. "It reflects the nature of this war. Not the lack of heroes."

The Medal of Honor, at the "tip of the pyramid" of honors available to U.S. forces, is meant to be awarded infrequently, Burrelli says. Troops receive the medal only for risking their lives in acts so courageous that failing to perform them would not trigger any criticism, he says. It is awarded by the president in the name of Congress and is often referred to as the Congressional Medal of Honor.

The Army's second top honor, the Distinguished Service Cross, has been awarded twice to soldiers in Iraq as of Dec. 27. Next is the Silver Star; 174 have been issued, according to the Army. In Afghanistan, there has been one Distinguished Service Cross and 37 Silver Stars. The Navy has awarded three Navy Crosses and 30 Silver Stars since Sept. 11, 2001.

In 1993 in Somalia, Army Master Sgt. Gary Gordon and Sgt. 1st Class Randall Shughart received the Medal of Honor posthumously. They protected critically wounded comrades whose helicopter had crashed in hostile territory in Mogadishu. Their heroism was depicted in the movie "Black Hawk Down."

There were no Medals of Honor awarded during the Gulf War. After weeks of bombing, allied ground forces whipped the Iraqi army in a 100-hour campaign.

The most recent act to merit the Medal of Honor came on April 4, 2003. On that day, Sgt. 1st Class Paul R. Smith, his position near the Baghdad airport nearly overrun, hastily organized a defense. Under fire, he climbed onto a damaged armored vehicle and attacked the enemy with a machine gun. He killed as many as 50 enemy soldiers and helped save the lives of 100 Americans.

On April 4, 2005, President Bush presented the Medal of Honor to Smith's widow, Birgit.

"It doesn't surprise me that more people haven't gotten it," she said. "It's so hard to do."