Ah, memories. Here is the background I gave my players for a campaign I ran a few years ago. The players started out very local in the most insignificant little backwater they could imagine (making Tatooine look like Coruscant by comparison), but in true Star Wars theme they went on to do glorious deeds on a grand scale. The campaign ended after the managed to infliltrate a super star destroyer variant as it was being retrofited to become a second Death Star, more mobile but with less firepower. The PCs managed to plant the explosives, fight off a major protagonist (the Jedi that trained the two force-sensetive PCs, now fallen to the dark side) and escape to the jungles of the prison moon below as the second Death Star went "super-nova". All through the campaign the only character they recognised was Admiral Ackbar. The rest are all dead...
Some say the rebellion was over before it really got going. Many who bear no love for the Galactic Empire and Emperor Vader claim the failure of the Jedis led to the downfall of the rebels and the final victory of the Empire. Parts of the story about the failure of the rebellion are public knowledge. Other parts are known to only a few.
What is commonly known is that after Chancellor Palpatine finally turned Anakin Skywalker to the dark side he sent his apprentice to destroy the Jedi temple on Coruscant, ordering him to slay anyone there. Even the youngest were not spared. Simultaneously the by now infamous Order 66 was issued, and the clones fighting the Clone Wars alongside the Jedis turned on the Jedis and killed most of them.
Only a handful of Jedis survived that day. The only two who managed to get back to the Jedi temple on Coruscant were master Yoda and master Obi-Wan Kenobi. After disabling the distress signal Darth Vader set in the Jedi temple they split up again. Yoda went to confront the Chancellor and Obi-Wan went after Darth Vader. Things did not go as planned.
After a furious battle with Chancellor Palpatine Yoda was overcome by the power of the dark side and slain. Obi-Wan fared better, and after fighting Darth Vader he defeated his former padawan, and left him to die. Obi-Wan then hurried to get Padmé, pregnant with Vader's twins, to safety.
The Chancellor, soon to be the Emperor, managed to save his pupil, and after Vader regained his strength he went after Obi-Wan with all his fury. Strangely Obi-Wan had chosen to hide away on Tatooine, a planet very familiar to Vader. There Vader confronted him four years after their first engagement. Vader had grown in power, and in the end he clove Obi-Wan in two, ending the life of his former master.
As the fight between Vader and Obi-Wan took place in the wastelands of Tatooine, word of his death was not spread beyond the neighboring settlements, especially since he had hidden his Jedi-powers from his neighbors. On the galactic stage many considered him dead anyway, so his death had little immediate effect. That changed 14 years later, when Princess Leia's ship was being pursued by Vader's Star Destroyer and she hid the plans for the Death Star on an astromech droid and sent it to find Obi-Wan.
Luke Skywalker knew of Obi-Wan (Ben), and knew he was dead. He eventually managed to get the message from Princess Leia out of the droid, and decided to join the rebellion. He set off to Alderan with the plans, flying on the Falcon with the crazy pilot Han Solo and his furry co-pilot.
Through shear luck (or perhaps clever design?) Luke and Han managed to rescue Princess Leia from the Death Star, get the plans to the rebel base, and set up a plan to take out the Death Star with a fighter attack. But as Luke had never really heard of the Force, let alone trained to use it, the attack ended in abysmal failure. All the fighter pilots, Luke included, were destroyed, and the Falcon shot down. The Death Star then targeted Yavin IV, the moon housing the rebel base, where Leia and a large group of rebels hid. They all died as the moon was disintegrated.
These were desperate times for the rest of the rebels. Friendly star systems defected from their cause out of fear of the Death Star. The remaining rebels decided that the time for extreme measures was upon them, and after leading the Imperial fleet on a merry chase to the far edge of the galaxy the rebels assembled every cruiser and fighter available to them and assaulted the Death Star head on.
The rebels knew that they did not stand a chance in a straight up firefight, so they went for the only option they hoped would destroy the Death Star. All capital ships were to try to get through the Death Star's impressive firepower and ram the space station at full speed, trying to hit the main superlaser's tributary beam emitters, hoping for a chain reaction that could destroy the Death Star.
They almost made it. Three cruisers managed to ram into the Death Star, and the captains were dead on when they targeted the beam emitters. Unfortunately for the rebels the Emperor himself was on the Death Star. Emperor Palpatine managed to use the Force to turn the Death Star on its axis. The cruisers struck the side of the Death Star instead of hitting the main weapon system, and although they inflicted massive damage, the Death Star was not destroyed. The battle station and incoming Star Destroyers of the Imperial fleet then destroyed the rest of the rebel fleet as the remaining ships attempted to disengage. The rebellion was over.
Saving the Death Star took everything Emperor Palpatine had, and when his apprentice, Darth Vader, reached his side he knew he had an opportunity he might not have again in a long time. Without hesitating Vader slew Emperor Palpatine with his lightsaber, and took over as Emperor.
The big rebellion might have failed, but eventually small groups of resistance fighters started to form in the far reaches of the galaxy. No longer hoping for a quick resolution and the end of the Empire most of the groups focused on surviving, training for the coming conflict, and taking whatever pot shots they could at the Empire's forces. Most of the groups operated independently, so that the capture of operatives from one cell would not compromise other cells.
Many thought the Jedis were finished. This was not far from the truth, but a handful had survived. When Darth Vader murdered everyone in the Jedi temple 20 years earlier a group of young initiates aged 10-12 were on a field trip. The librarian in the Jedi temple managed to warn the pilot of their shuttle before Vader got to the center of the temple. The pilot wisely fled with the young initiates. After consulting Obi-Wan the pilot, alone with the Jedi children, decided to scatter the survivors throughout the galaxy to prevent the Emperor from hunting them down and slaying the last remaining Jedis in one fell swoop.
None of the young initiates were even close to being fully trained as Jedi Knights. They all tried their best to hone their abilities and learn new ways to use the force. All realized that there were mysteries hidden to them that used to be common knowledge to the Jedis. Many ended up focusing on few powers, whereas the old Jedis preached that every Jedi should be trained in as many aspects of the Force as possible. Several fell to the dark side without the guidance of the more experienced Jedi.
Some focused on the martial side of the force, precognition and lightsaber fencing. Others focused on moving objects with the force, while yet others had some ability to deceive the weak-minded. One of the secrets lost to most, if not all, was the secret to making lightsabers. This made the ancient weapons of the Jedis hard to get for the apprentices of those unlikely Jedi masters, and the secret of making them highly sought after.
The young Jedis nonetheless took on promising apprentices and trained them, but much knowledge had been lost. The power of a single Jedi, formerly able to lead assaults into blaster fire, lift starfighters with a single thought or healing the bodies through the Force, had become much less than what it used to be.
On Coruscant things were going in the opposite direction. Appreciating the value of Sith as enforcers and agents Darth Vader re-opened the Jedi temple, but re-focused it to teach the Dark Side of the Force, ignoring the tradition of Sith working only in groups of two, apprentice and master. Most of his Sith apprentices are individually far more skilled than the surviving Jedis, having most of the knowledge of their master at their fingertips, as well as the undeniable power of the Dark Side. Most assume that Vader has been careful in deciding what to teach his pupils and what to keep for himself to ensure his growing army of Sith does not betray him.