Republic

The Galactic Republic, commonly referred to as the Republic and later known as the Old Republic, was the democratic union that governed the galaxy for a thousand years prior to the rise of the Galactic Empire. Centered on the Core World of Coruscant, the Galactic Senate—a body of legislators who represented the numerous planets throughout the galaxy—governed the Republic under the leadership of the democratically elected Supreme Chancellor. Throughout its history, the Republic was protected by the [Order] , an organization of Force-sensitives who served as the guardians of peace and justice, enabling the Republic to be free of full-scale conflict for most of its existence. However, thirty-two years before the Battle of Yavin, the Republic suffered its first major crisis in a millennium during the invasion of Naboo by the Trade Federation, which ultimately led to the Clone Wars a decade later.
During this galaxy-wide conflict, the Republic underwent a massive military buildup beginning with the mobilization of the Grand Army of the Republic—an army of clone troopers, bred for war and led by the Jedi . As the war carried on, the Senate's authority was gradually eroded by the increasing power of[Chancellor Palpatine| Supreme Chancellor Sheev Palpatine] . Unbeknownst to all but a select few, Palpatine was in reality the Dark Lord of the Sith Darth Sidious, and had engineered the crisis to overthrow both the Republic and the Jedi, effectively doing so nineteen years before the Battle of Yavin. After the Jedi learned of his true nature, Palpatine enacted Order 66, a secret protocol that forced the clones to betray and execute their Jedi officers, effectively wiping away the Jedi Order in an instant. With the fall of the Jedi and the restoration of Sith dominance, Palpatine brought an end to the thousand-year Republic by proclaiming the formation of the First Galactic Empire. The newly-anointed Emperor Palpatine preserved the Senate for a further two decades, but ultimately disbanded the last remnant of the Old Republic upon the completion of the Death Star.
Within four years of the Senate's dissolution, the Empire suffered the loss of two battle stations and the death of Emperor Palpatine. The Alliance to Restore the Republic subsequently reformed itself as the New Republic and ultimately claimed victory in the Galactic Civil War approximately one year after the Emperor's demise.