Montmartre, whose brilliant four-length victory in the Grand Prix de Paris last July 14 propelled him into summerlong co-favoritism with stablemate Zarkava for the Prix de l'Arc de Triomphe, was retired by his owner, the Aga Khan, on Wednesday.\nBy Arc and King George winner Montjeu out of 1 7/8-mile, Group 3 Prix Berteux winner Artistique, he sustained a leg injury in the Grand Prix and was put away for the year in September. A setback earlier this week prompted his retirement.\nTrained by Alain de Royer-Dupre, Montmartre was rated at 125 on the 2008 World Thoroughbred Ratings, the same as fellow 3-year-olds Big Brown, Conduit, Goldikova, and Henrythenavigator. A disappointing 15th in the 1 5/16-mile Prix du Jockey-Club (French Derby), he improved when stretched out to 1 1/2 miles, winning the Group 3 Prix du Lys and the Group 1 Grand Prix de Paris. Bred in France by S.N.C. Lagardere Elevage, Montmartre won 3 of 5 starts for earnings of $637,598.