Complex sentence: Smythe is also known for having served in both World Wars, organizing his own Battery in World War II. The horses of Smythe's racing stable won the Queen's Plate twice among 145 stakes races wins during his lifetime.
Split into simpler sentences: Smythe is also known for having served in both World Wars, organizing his own Battery in World War II. Smythe was successful in horse racing as a racing stable owner. His horses won the Queen's Plate twice among 145 stakes races wins during his lifetime.