The Alliance to Restore the Republic (2 BBY–4 ABY), commonly known as the Rebel Alliance, Alliance, the Rebellion, and rarely the Separatists, was a resistance movement formed by Bail Prestor Organa and Mon Mothma to oppose the reign of the Galactic Empire. The Alliance was formed from a less organized movement to oppose the Empire that existed, which was secretly led by Organa. This early group came together from a number of rebel cells, including the crew of the Ghost and the Phoenix Cell. The Atrivis Resistance Group was one of the first cells to join what Mothma began calling "the Alliance" before the formal formation of the Alliance to Restore the Republic. The Alliance was publicly and formally declared with the Declaration of the Rebel Alliance.
The Alliance and the cells before it were born from the overall discontent within the Empire of those who wished the Old Republic restored. Its efforts were led by renegade members in the Imperial Senate such as Mon Mothma, Bail Organa, and later, his daughter Leia Organa, and its members were citizens of the Empire and defectors from the Imperial Military such as Jan Dodonna, Ryder Azadi and Wedge Antilles. Founded and united by Organa and Ahsoka Tano, the early rebels were assisted by surviving Jedi who turned good, such as Kanan Jarrus, and his Padawan, Ezra Bridger. Clone Wars veterans such as Captain Rex also assisted in the initial movement.
As opposed to waging all-out war, the Alliance waged a war of attrition against the Empire, establishing small bases across the galaxy instead of controlling an entire planet.
When the Alliance stole the plans for the Empire's ultimate weapon, the Death Star, and destroyed the space station in the Battle of Yavin with the help of Luke Skywalker, the tide of the war began to turn, and the Rebel threat began to prove a severe thorn in the Empire's side. The Rebellion continued to engage in battles with the Empire in the Galactic Civil War. However, under the command of Darth Vader, the Imperial forces succeeded in defeating the Alliance on Hoth, forcing the Alliance to scatter its forces in order to survive.
Eventually, the Alliance prevailed against the Empire and critically damaged it by launching an attack against the second Death Star during its construction in what would become the Battle of Endor. Not only did the Alliance manage to destroy the battle station, but the Imperial Navy was severely crippled by the loss of one of its Super Star Destroyers, and Luke Skywalker redeemed his father, Darth Vader, who killed Emperor Sheev Palpatine, before dying himself in the battle. The Alliance was soon reorganized into the fledgling New Republic, which went on to defeat the Empire at the Battle of Jakku one year after Endor and force the Empire to surrender by signing the Galactic Concordance, effectively ending the war.
By the time of the Battle of Yavin, the Rebel Alliance had chosen a red starbird as its symbol and logo.