The First Order Emerges
The New Republic would survive for nearly 3 decades, but drawn out senatorial debates quickly made some (historically privileged) systems look back on the days of the Empire's brutal efficiency with rose-colored glasses. Sure, the man commanding the might of the Empire was a tyrant, but what if that same kind of power was given to someone more benevolent? Could the frequent impasses seen in the Senate be totally avoided by a stronger central authority?
Obviously not all systems see eye to eye on this part, with many formerly oppressed peoples greatly appreciating having a voice for the first time in a generation. This growing split results in two factions: the populists, who want power vested in individual systems and planets, and the centrists, who want power centralized in a single figurehead. While the war rages on in the Senate, some centrist systems begin funneling money through a crime syndicate into the pockets of a resurgent Imperial faction, living in the Shadows as the First Order.
Narrowly surviving a bombing at the New Republic Senate, Leia Organa investigates a cartel she believes could be involved, uncovering ties to a massive military group, revealing there is a quickly growing threat to the New Republic. The immediate threat is subdued, but the New Republic refuses to raise a proper defense force in response, preferring to stay non-militarized as it has been since the fall of the Empire.
Birth of the Resistance
Since the New Republic won't defend itself, Leia Organa retires from government duty to form the Resistance, along with a few old Rebellion heroes such as Gial Ackbar and Caluan Ematt. The Resistance is the galaxy's first - and basically only - line of defense against the new threat of the First Order. While Leia is able to muster minimal support, the Resistance still struggles to grow, benefiting from the addition of a number of tactical geniuses and crack pilots like Admiral Ackbar and Black Squadron leader Poe Dameron.
Fall of the Jedi
Having taken his nephew, Ben Solo, on as one of many new apprentices, Luke believes the boy has potential to be a powerful Jedi. While Ben initially proves to be adept with the Force, he's eventually swayed to the dark side by The First Order's mysterious Supreme Leader Snoke. He turns on Luke, killing destroying the new generation of Jedi. Taking the name Kylo Ren and becoming the master of the Knights of Ren, the former son of Solo is now a ruthless attack dog of the First Order.
Devastated and ashamed at his failure and the loss of the Jedi, Luke goes into exile, seeking out the location of the first Jedi temple on the planet Ahch-To.