Sun Briar's dam was Sweet Briar, a French daughter of Leopold de Rothschild's St. Frusquin, whose wins included the Classic 2,000 Guineas Stakes and who was the Leading sire in Great Britain and Ireland in 1903 and 1907.

[3] Voted the 1925 American Champion Two-Year-Old Colt,[4] Pompey was an early favorite to win the 1926 Kentucky Derby.

In his 1926 season debut, Pompey won the May 1st Wood Stakes at New York's Jamaica Race Course.

On May 15, Pompey was sent off as the second choice by bettors in the Derby at Churchill Downs in Louisville, Kentucky.

[9] At age four, Pompey competed with some success, winning the August 1, 1927 Inaugural Handicap at Saratoga Race Course[10] and on August 23 running the fastest six furlongs of the Saratoga summer meet with a time of 1:11 2–5 while winning the Blue Mountain Handicap.