One runner is one of four men in U.S. history to have competed in five Olympic marathon trials. Another is a masters record holder and three-time masters winner of the race. Then there are two veterans of the war in Iraq: a major who just returned and a woman who lost her right arm.

They are among the 20,000 runners registered for Sunday's Army Ten-Miler.

Billed as the largest 10-mile road race in the country and the second largest in the world, the 21st annual event features runners from 50 states and the District as well as more than 100 international runners from 27 countries. The race begins at 8 a.m. at the Pentagon, loops around the monuments and the National Mall, then concludes back at the Pentagon.

Although last year's male and female winners -- three-time event champion Dan Brown, who set the course record of 47 minutes 32 seconds in 2004, and Casey Smith (57:32) -- are not running, the race features several notable runners.

Darrell General, 39, from Hyattsville, has competed in five Olympic marathon trials, finishing in 2:33:20 in February 2004. The track coach at Marshall High School is a two-time winner of the Army Ten-Miler.

Martha Merz, 42, of Mystic, Conn., holds the event masters record of 59:49, set in 2002, and is a three-time masters winner. Major John Nolan of Lake Ridge returned from Iraq in June. Nolan has run in nearly every Army Ten-Miler since 1989. Nearly a third of the runners are active military personnel.

Dawn Halfaker, a retired Army captain and 2001 West Point graduate, was one of the first women to lose a limb during combat in Iraq. Halfaker is the team captain for Missing (Parts) in Action, a group of military amputees running in the race. She lost her right arm after a rocket-propelled grenade exploded inside her Humvee.

-- Kathy Orton