A riderless horse or caparisoned horse (in reference to its ornamental coverings, which have a detailed protocol of their own) is a single horse, without a rider, and with boots reversed in the stirrups, which sometimes accompanies a funeral procession. The horse follows the caisson carrying the casket. A riderless horse can also be featured in military parades to symbolize fallen soldiers. In Australia for example, it is traditional for a riderless horse known as the 'Lone Charger' to lead the annual Anzac Day marches.
The custom is believed to date back to the time of Genghis Khan, when a horse was sacrificed to serve the fallen warrior in the next world. The caparisoned horse later came to symbolize a warrior who would ride no more. 
In the United States, the caparisoned horse is part of the military honors given to an Army or Marine Corps officer who was a colonel or above; this includes the President, by virtue of having been the country's commander in chief and the Secretary of Defense, having overseen the armed forces. Alexander Hamilton, former Secretary of the Treasury (1789-1795) was the first American to be given the honor. Historian Ron Chernow noted that Hamilton's gray horse followed the casket "with the boots and spurs of its former rider reversed in the stirrups." Abraham Lincoln was the first president of the United States to be officially honored by the inclusion of the caparisoned horse in his funeral cortege, although a letter from George Washington's personal secretary recorded the president's horse was part of the president's funeral, carrying his saddle, pistols, and holsters. Traditionally, simple black riding boots are reversed in the stirrups to represent a fallen leader looking back on his troops for the last time.
In 1865, Abraham Lincoln was honored by the inclusion of a caparisoned horse at his funeral. When Lincoln's funeral train reached Springfield, Illinois, his horse, Old Bob, who was draped in a black mourning blanket, followed the procession and led mourners to Lincoln's burial spot.
A notable riderless horse was "Black Jack," a half-Morgan named for General of the Armies John "Black Jack" Pershing. Black Jack took part in the state funerals of Presidents John F. Kennedy (1963), Herbert Hoover (1964), and Lyndon Johnson (1973), and General of the Army Douglas MacArthur (1964).
Black Jack was foaled January 19, 1947, and came to Fort Myer from Fort Reno, Oklahoma, on November 22, 1952. Black Jack was the last of the Quartermaster-issue horses branded with the Army's U.S. brand (on the left shoulder) and his Army serial number 2V56 (on the left side of his neck). He died on February 6, 1976, and was buried on the parade ground of Fort Myer's Summerall Field with full military honors, one of only two US Army horses to be given that honor.
"Sergeant York" was formerly known as "Allaboard Jules", a racing standardbred gelding. He was renamed (in honor of famous WWI soldier Alvin C. York) when he was accepted into the military in 1997. He served as the riderless horse in President Ronald Reagan's funeral procession, walking behind the caisson bearing Reagan's flag-draped casket.
He was foaled in 1991, sired by Royce and out of the mare Amtrak Collins sired by Computer. He is a descendant of the great standardbred racing stallions Albatross, Tar Heel and Adios.
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- "Arlington’s Ceremonial Horses and Funerals at the White House" (PDF). White House History.org. Retrieved 28 April 2010.
- Knuckle, Robert (2002). Black Jack: America's famous riderless horse. General Store Publishing House. p. 4. ISBN 9781894263658.
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