The New Jedi Order was the restored and reformed Jedi organization, in the wake of the Great Jedi Purge and subsequent fall of the Galactic Empire. The Jedi Knights, reduced in number to only a handful, were slowly restored, primarily under the leadership of Luke Skywalker, son of the former Jedi Knight Anakin Skywalker.
Slow in developing, it existed for a number of years as a disparate group of Force-sensitives with various degrees of training. After a first attempt to train new Knights was foiled by the Reborn Emperor, Luke Skywalker initiated the first formal training school for Jedi in decades, the Jedi Praxeum on Yavin 4. Starting with an initial group of 12 students, the Order slowly grew in numbers and stature, becoming a core part of the New Republic that sponsored it. This meant it was repeatedly targeted by enemies of the Republic, such as Admiral Daala, the Empire Reborn, and the Second Imperium. Members of the order were involved in many of the key conflicts in the galaxy, including the Nagai-Tof War, Operation Shadow Hand, the Black Fleet Crisis and the First Corellian Insurrection.
This involvement culminated in the Jedi involvement in the Yuuzhan Vong War. Committed to defending the galaxy from this threat, the Order was vilified by the galactic citizens and was betrayed on numerous occasions. Their involvement in the war cost nearly half the Order’s Knights. Out of this conflict, a more ruthless, and later, centralized Order was born. It would continue to grow and serve the galaxy for decades to come, until the Sith–Imperial War once again dispersed the Order and made its members fugitives. They subsequently returned to their place in the Galaxy at the end of the Second Imperial Civil War.