Complex sentence: American Pharoah (foaled February 2,2012) is an American Thoroughbred racehorse who won the American Triple Crown and the Breeders' Cup Classic in 2015, becoming the first horse to win the "Grand Slam" of American horse racing.
Split into simpler sentences: American Pharoah (foaled February 2,2012) is an American Thoroughbred racehorse who won the American Triple Crown and the Breeders' Cup Classic in 2015. IN winning all four races, he became the first horse to win the "Grand Slam" of American horse racing.