The Grand Army of the Republic (GAR), also known as the Republic Army, the clone army, or the Galactic Army, was the army branch of the Republic Military throughout the duration of the Clone Wars. At the time of the First Battle of Geonosis, the Galactic Republic activated tens of thousands of clone troopers to fight the Separatist Droid Army of the Confederacy of Independent Systems. In addition to human clones, all grown from the bounty hunter Jango Fett‘s genetic template, the Grand Army consisted of various military vehicles for ground support, including AV-7 Anti-vehicle Artillery Cannons, BARC speeders, and All Terrain Tactical Enforcers.
During the final years of the Republic, Jedi Master Sifo-Dyas contacted the government of Kamino to commission the creation of a clone army, convinced that the galaxy would be consumed by war. As thousands of star systems joined the Separatist movement, the Galactic Senate invested wartime powers in Supreme Chancellor Sheev Palpatine. As a result, the Grand Army of the Republic was formally established, comprising thousands of clone soldiers with millions more being developed in Kaminoan facilities by the start of the Clone Wars. The Jedi Knights, having served as peacekeepers for a thousand years, became Jedi Generals when the Senate called on the Jedi Order to lead the Grand Army against the enemies of the Republic.
For three years, the Grand Army fought on all fronts across a war-torn galaxy, from the campaigns in the Outer Rim Territories to a Separatist attack on the Republic capital of Coruscant. Through the machinations of Palpatine, revealed to the Jedi as the Sith Lord Darth Sidious, the clones would ultimately turn against their Jedi leaders, slaughtering them throughout the galaxy and in the Jedi Temple as directed by Order 66. After Sidious declared himself Emperor of the Galactic Empire, the Grand Army of the Republic was absorbed by the New Order and reorganized into the Imperial Army, allowing the remaining clone troopers to serve as the first generation of stormtroopers.