Man of Iron has won the $500,000 Breeders' Cup Marathon in a photo finish over 9-year-old gelding Cloudy's Knight.

Man of Iron won by a nose Friday in the first race of the two-day world championships at Santa Anita. Irish trainer Aidan O'Brien earned his fourth career Breeders' Cup win.

Ridden by John Murtagh, Man of Iron paid $14.80, $7.20 and $4.40 in his U.S. debut after running exclusively in Europe. The 3-year-old colt covered 1 3/4 miles in 2:54.11 on the synthetic Pro-Ride surface.

Making his Breeders' Cup debut at the relatively advanced age of 9, Cloudy's Knight returned $7.40 and $4.60. Mastery was another 2 1/4 lengths back in third and paid $2.40 to show.

Gangbuster was fourth in the field of 10.