The Rebel Alliance was a terrorist organization that was bent upon the removal of the lawfully elected Emperor and the destruction of the Empire as a whole. The stated goal of the Rebel Alliance was to restore the Republic which had previously failed to stop a galaxy wide war and been proven to be a corrupt mess controlled by the commerce guilds instead of the peoples of the galaxy.
First Major Terrorist Act
For the first five years of the Alliance there were very little in the way for success stories. However they then obtained knowledge of the Dynasty Class space station (DS-1) which they code named Death Star. When Alderaan declared itself at war with the Empire and attacked the nearby station It defended itself. The Rebel alliance used this as justification for their impending terrorist attack. Lead to Yavin under the false pretenses of peace talks, the Rebel Alliance lead an attack on the DS-1. Luke Skywalker fired the shot that destroyed DS-1 killing over 1 million Imperial officers, personnel and private citizens. That this genocidal "Jedi" was held to be a hero of the rebellion tells you much about their true nature.
After the descruction of the DS-1 the Emperor decided that his attempts at a peaceful resolution would be for naught. He assigned Darth Vader, one fo the few survivors of the Yavin terrorist attack, the task of removing the Rebel threat. Vader, previously successful in eliminating the Jedi threat to peace, began in earnest and quickly had the Rebel Alliance on the run. After a great victory at Hoth and the successful capture of Han Solo, one of the leaders of the Alliance and confidant to Luke Skywalker, the rebels were forced further underground.
Attack on the Emperor
The emperor in an attempt to calm the fears of the populace decided to build another Dynasty Class Space Station the DS-2. In an attempt to ease fears and instill a sense of security to those working on the new space station, The Emperor personally oversaw its completion along with his most trusted advisors and best military minds. The rebel alliance saw this as an opportunity to strike fear across the Galaxy and make their grab for power. They hijacked a transport ship and removed the shielding for the station. It is believed that Luke Skywalker allowed him self to be captured and taken to the DS-2 so that once the shielding was removed he could cause an internal explosion along with surprise attack of the entire rebel fleet. The daring plan was successful and resulted in the death of the Empire, Lord Vader and many of the best and brightest of the Empire. Again Skywalker was responsible for the deaths of millions of innocent lives.