What Does It Mean To Be A Sire In Thoroughbred Racing

by Anne B. Robinson

“Sire,” in racing terms, is a word that can be commonly used as both a noun and a verb. It can refer to the act of fathering a horse (such as “Keen Ice sired Kentucky Derby winner Rich Strike”), or it can refer to the horse that does the fathering (such as “Nest’s sire is Gun Runner”).

However, in a sport so meticulously documented over centuries as horse racing, the term “sire” has evolved to encompass direct male-line ancestry. In addition to a horse’s direct parentage, there are “foundational sires” of specific regions, sire lines, and the breed itself.

Foundational Sires of the Thoroughbred

The modern Thoroughbred breed was developed by three key stallions: the Byerly Turk, the Darley Arabian, and the Godolphin Arabian (sometimes referred to as the Godolphin Barb). Every Thoroughbred in the world today traces to at least one of these stallions, and most have all three at multiple spots in their pedigree.

When looking at surviving sire lines alone, the Darley Arabian dominates. This is due in large part to his descendant Phalaris, who is the direct male ancestor of most modern Thoroughbreds, including almost all of the stallions mentioned in this article.

A few direct male-line descendants of the Godolphin Arabian remain prominent, mostly through the Man o’War line. The Byerly Turk sire line dwindled greatly during the twentieth century and no longer has much influence, but the Byerly Turk himself is still a near-ubiquitous presence elsewhere in Thoroughbred pedigrees.

Popular 20th-Century Sire Lines


Phalaris, a direct descendant of the Darley Arabian, is the male-line ancestor of up to 90% of today’s Thoroughbreds. A 1913 son of Polymelus and the mare Bromus, by Sanfoin, Phalaris was a top sprinter-miler for the 17th Earl of Derby. He won 16 of 24 starts as a racehorse, running from ages two to five.

At stud, Phalaris was a huge speed influence and combined well with mares from stamina-based pedigrees, in particular daughters of the sire Chaucer. Four of Phalaris’s sons created sire lines that are still prominent today: Sickle (ancestor of Mr. Prospector), Pharamond II (ancestor of Buckpasser), Pharos (ancestor of Northern Dancer), and Fairway (ancestor of prominent sires in South America).

Man o’War

The Man o’War sire line is what has kept the direct male line of the Godolphin Arabian alive into the twenty-first century. Man o’War was quite possibly the best American Thoroughbred racehorse in history, and he sired several fantastic runners as well, including Triple Crown winner War Admiral.

However, it was his son War Relic who provided his most enduring sire line. Modern sires who trace back to War Relic include dual Breeder’s Cup Classic winner Tiznow and Brazilian Triple Crown winner Bal a Bali.

Modern Foundational Sires in North America/Europe and Japan


Nasrullah, who traced to Phalaris through his son Pharos, was a talented but foul-tempered racehorse who was one of the most influential imported stallions the United States has ever stood.

His son, Bold Ruler, became the sire of the immortal Secretariat, but it was through his connection to Seattle Slew and A.P. Indy that his sire line survived. A.P. Indy produced the good sires Bernardini, Malibu Moon, Honor Code, and Pulpit, whose son Tapit is one of the hottest sires of the last decade.

Northern Dancer

Northern Dancer was another descendant of Pharos. The most renowned horse to come out of Canada, Northern Dancer became the first (and thus far only) horse to win both the Queen’s Plate and the Kentucky Derby. Northern Dancer was an immediate success at stud, siring champion Vice Regent in his first crop and English Triple Crown winner Nijinsky II in his second.

He proved a successful influence on both American (dirt) racing and European (grass) racing, establishing dominant sire lines worldwide. His current descendants at stud include Galileo, Teofilo, Frankel, and American Triple Crown winner Justify.

Mr. Prospector

A descendant of Sickle, Mr. Prospector, was a sprinter who initially stood at stud in Florida, before being moved to Kentucky because of his immense success. His most successful offspring include champions Forty Niner, Gulch, and Conquistador Cielo, but possibly his most influential son was Fappiano, ancestor of American Triple Crown winner American Pharoah.

Sunday Silence

Sunday Silence was unheralded at the beginning of his racing career, but by the end of 1989, no one could deny that he had the heart of a champion. However, he did not have the fashionable bloodlines of his most famous rival, Easy Goer, and there was little demand for his services at stud when he retired in 1990.

Teruya Yoshida was able to purchase Sunday Silence to stand at the Shadai Stallion Station, and that purchase alone forever changed the Japanese Thoroughbred industry. Sunday Silence eventually sired six Japanese Derby winners, seven Japanese 2000 Guineas winners, four Japanese St. Leger winners, and three Japanese 1000 Guineas winners.

His influence continues to be felt not only in Japan but throughout the world, with current representatives at stud including Saxon Warrior, Silent Name, and Yoshida.

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