The Emperor took a young pilot and hero of the Clone Wars named Anakin Skywalker him under his wing. Noting the young man's strong potential with the Force, Palpatine swayed Skywalker to the Dark Side, and soon Skywalker took the name Darth Vader and become the Emperor's chief emissary. With Lord Vader's assistance, the Emperor began a galaxy-wide purge, all but eliminating the order of the Jedi, protectors of the corrupt Old Republic. With the Jedi extinct, the Emperor's attention turned to a new project: the Death Star. Brought to his attention by Tarkin, one of his Grand Moffs, the Emperor embraced the "rule by fear" doctrine, which proposed that the galaxy should not be ruled by force but by threat of force. The Imperial Navy rose in power and galactic prestige; the Imperial-Class Star Destroyer became a symbol for Imperial power throughout the stars.
When construction on the Death Star, an armored space station with enough firepower to destroy an entire planet, lagged, the Emperor, out of patience, sent his emmissary Lord Vader to "motivate" the workers. Soon the Death Star was finished, and, under Tarkin's command, destroyed the rebellious planet Alderaan as an example to would-be rebels. But when the Death Star was destroyed, Palpatine became aware of a young pilot for the Rebel insurgence named Luke Skywalker. Realizing that any offspring from a warrior as powerful with the Force as Lord Vader could be a threat to him, Palpatine gave Lord Vader command of a Star Destroyer attack fleet, and ordered him to bring in Skywalker. If Skywalker would not turn to the Dark Side, he would be destroyed.
Not until the Battle of Endor, aboard the second Death Star battlestation, did the Emperor confront Luke Skywalker. Though he tried to drive the boy through anger, fear, and aggression to the Dark Side, the boy would not yield. Resigned, the Emperor began to use Dark Force lightning to kill young Skywalker. But the Emperor had not forseen betrayal from his second-in-command, and after pleading from Luke, Lord Vader could not watch his son die. He hurled the Emperor down the Death Star's main reactor shaft in order to save his son. Emperor Palpatine died in an explosion of Dark Side energy, and the Empire was thrown into disarray.
However, five years later, Grand Admiral Thrawn, possibly the most brilliant military leader in the history of the Galaxy, returned from an extended mission in the unknown regions, gathered the remnants of the Imperial Fleet, and started to turn the war back against the rebellion, which had started calling itself the "New Republic." Unfortunately, due to the treachery of the Noghri, thought to be loyal to the Empire, Grand Admiral Thrawn was killed and the Empire was thrown back even further.
A year later, the Emperor returned in a new clone body. He revealed that he had cloned himself many times before, discarding old, worn-out bodies for young, strong ones. Thus, his 'death' aboard the second Death Star was not a big deal for him. He once again tried to turn Luke to the Dark Side, and succeeded, but unfortunately Luke's sister brought him back to the Light Side. They then murdered the reborn Emperor and destroyed his cloned body. Thus ended the rule of a great leader.
The Empire still struggles to restore the order that the Galaxy was once blessed with, but without a great leader like the Emperor or Thrawn, it is a disorganized shadow of its once great self.