During the New Sith Empire, Draggulch Period
Around 1,100BBY
The Republic Dark Age was the term given to the last century of the Draggulch Period, from around 1,100 BBY to the Ruusan Reformation of 1,000 BBY. During the Dark Age, the Republic, in the eyes of later centuries, had essentially ceased to exist.
Since the start of the Draggulch Period in 2,000 BBY, the Republic had been in decline. During the series of conflicts known as the New Sith Wars, thousands of worlds were abandoned to the New Sith Empire, while more were abandoned during the Republic's retreat. Thousands of longstanding corporations went bankrupt; lawlessness spread as the Republic government became increasingly overburdened and ineffectual; and numerous mines of valuable minerals dried up. The collapse escalated following the Sith victory at the Battle of Mizra in 1,466 BBY.
However, all these events were merely a prelude to the Dark Age. The Senate granted almost all of its authority to the Supreme Chancellor, many of whom were Jedi at that point. The Jedi themselves wielded near-unlimited power. Although the unity of the Sith seems to have been broken by infighting, and the ongoing conflict was officially portrayed as merely a series of clashes against an illegal organization, the situation wore down the Republic Navy and Army, which likewise fell under increasing Jedi control.
The Republic could no longer afford to maintain the HoloNet beyond the Core Worlds, so communications between worlds outside the Core had to be maintained through couriers. Even worse, a galaxywide epidemic of Candorian plague killed off as much as two-thirds of the population of some worlds.
As already noted, it seems that the threat from the Sith may have been much diminished compared with previous centuries, but at the end of this period, around 1,010 BBY, a former Jedi Master named Lord Kaan reorganized the feuding Sith into the Brotherhood of Darkness, and embarked on the last of the New Sith Wars, sometimes known as the Light and Darkness War. Republic forces led by commanders like Hoth, a Jedi Master and General, won some notable victories, initially driving Kaan's forces from their stronghold in the Cloak of the Sith, but the Sith reconquered their ancient capital on Korriban, and also struck deep into the Core Worlds.
For the final two or three years of the war, however, much of the attention of the Jedi and Sith was focused on the planet Ruusan, near Kashyyyk, where the entire Brotherhood of Darkness fought the Jedi who Hoth had formed into the Army of Light in a protracted series of engagements.
Presumably, the Dark Age was considered over by either the Sith defeat at the Seventh Battle of Ruusan, or the following Ruusan Reformation.
Tatooine is rediscovered.
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Star Wars - Unforeseen
1,100 cycles before the battle of Yavin...
The Interview
Everyone sat motionless. There was a slight rain outside that provided the only sound to be heard, other than Mear Bhall's heartbeat.
The rediscovery of Tatooine had been an afterthought to the Republic, just another rock in the Outer Rim that had barely enough life on it to warrant any investigation. But the sudden realization that a Sith cult had taken Tatooine as its home, changed everything. It became a top priority. Jedi Knight Bhall was tasked with the investigation, and had travelled to Tatooine to ascertain exactly what was going on. Nothing had gone as planned. Now he sat before the Jedi Council and awaited the order to give his report.
Of the 100 members of the Council, the three that sat before him, held the most power in the Senate. By their word, wars would be fought in the fashion they saw fit. At this time, the Jedi held most positions of power in the Republic. To them, the responsibilities of maintaining peace and order fell, and with the threat of the Sith closing every moment towards the Core Worlds... No one doubted their wisdom. The three Masters that sat before Mear were all humanoid, but other than that, they couldn't have been more different.