Galactic Empire (Star Wars)
In the fictional Star Wars universe, the Galactic Empire was the regime established by Palpatine to replace the Galactic Republic.The Republic ended following a period of intense political turmoil and war. At the height of the chaos the Republic's scheming head of government, Supreme Chancellor Palpatine, proclaimed himself Emperor.
The Empire was ruled with absolute power by Palpatine as Emperor with Darth Vader being his assistant. The Galactic Senate still existed years after the Empire's establishment, but it had little power and was eventually dissolved by Palpatine. The real power below the Emperor was in the hands of the Grand Moffs, like Tarkin and the regional governors who were eventually granted direct control of their regions.
The Galactic Empire was actually more decentralized than its immediate predecessor, the Galactic Republic. Much more power was sent into the hands of the Moffs and Grand Moffs who controlled regional issues. This is in contrast to the structure of the Old Republic, which apparently had no intermediary between low-level planetary affairs and that of the Galactic Senate itself.
This power was backed up by the use of state terrorism which threatened horrific retaliation to any defiance to the government. The instrument of that terror was the Imperial military, which included the Imperial Stormtroopers and a large fleet of intimidating war vehicles like Star Destroyers and All Terrain Armoured Transports (AT-ATs or Walkers) which were intended in part to spread fear as well as destroy the enemy.
In addition a key instrument was intended to be the Death Star, a moon sized space station with sufficient firepower to destroy a planet with a single shot, shown in the first Star Wars movie, .
In the Expanded Universe, the Empire also emphasized humanoid supremacy, with other alien species like Wookiees subject to slavery. This attempts to explain why almost everyone on the side of the Empire in Episodes IV, V, and VI is human, and usually have a British accent. It is believed by some that Palpatine's association with non-humans like Darth Maul in contradicts the idea that there is any humanoid bias on the part of Palpatine.
The Empire was opposed by the Rebel Alliance, a guerilla army dedicated to the defeat of the Emperor and the restoration of the Galactic Republic. This goal was nominally achieved with the death of Palpatine and the destruction of the second Death Star at the hands of the Alliance at the Battle of Endor, as depicted in the sixth Star Wars movie, . However, the Empire was too large to be destroyed in one blow; for the next decade and more, the Rebels, renamed the New Republic, fought to free the galaxy from former Imperials styling themselves as independent warlords as well as Imperial loyalists such as Grand Admiral Thrawn. These battles are chronicled in the many novels licensed by Lucasfilm.
The last gasp of the Empire was the Imperial Remnant, a shadow of its former glory.
An interesting article supporting the Empire can be found at The Case for the Empire. A response to that article is No Case for the Empire.
See also: Isaac Asimov's Galactic Empire Series