The Army of the Republic was created by the cloners on Kamino, and comprised of ten thousand clone troopers and their war machines, as of the start of the Clone Wars. After the initial engagements, a million more clone troopers were added to the ranks of the army.
The creation of the army was apparently ordered by Jedi MasterSifo-Dyas, though it was actually part of a plot concocted by Darth Sidious to craft an army for the Sith Lords. Though the clone troopers fought for the Republic during the Clone Wars, the army was turned against the loyalists and the Jedi at the war's end. Chancellor Palpatine wielded executive control over the army, and transformed it into the military of his Galactic Empire.