Thrawn campaign

The Thrawn campaign was a series of innovative military and political manuevers executed by Grand Admiral Thrawn in 9 ABY. Thrawn's attacks, feigns and policies constituted the first major internal and external conflict for the New Republic, and nearly succeeded in toppling the fledgling government.

Preliminary Stages
In 9 ABY, Thrawn emerged from the Unknown Regions, consolidated the remnants of the Galactic Empire, began an ambitious series of technological upgrades and developments, and planned his reconquest of the galaxy. Thrawn viewed his strategy as a series of interlocking pieces that added up to "the only puzzle world solving...the complete, total, and utter destruction of the Rebellion". As such, he began his campaign with a raid on Obroa-skai to learn the location of Myrkr, to acquire the ysalamiri, and Wayland, to acquire Joruus C'baoth and the cloaking device of Mount Tantiss.

Imperial Intrigutes
While Thrawn proved to gain strategic and tactical superiority with a smaller force, his moderate armada did not represent the full strength of the Imperial remnants. The clone Emperor, already consolidating power on Byss, ordered most of the Imperial forces to ignore Thrawn and return to the Deep Core. It is unclear if Palpatine intended for Thrawn to be a distraction while he continued to rebuild his strength, or if his extended out-of-body period effected his mind to the point of considering Thrawn as a threat rather than a loyal officer.

Conclusion
The Battle of Bilbringi marked the conclusion of the Thrawn campaign. As the fallen leader's forces fell into retreat, the New Republic was allowed a brief respite before the reborn Emperor would emerge to launch another near-fatal assault. To quote Admiral Ackbar's analysis of New Republic military losses, "The [New Republic] sustained considerable losses in the Thrawn campaign: ten percent of our forces killed, thirty percent wounded -- but those are just averages. On the worlds Thrawn actually hit, the devastation was significant." In addition, the campaign further fractured the body of the New Republic, giving rise to Borsk Fey'lya's political career.

On the other side, the campaign led to the creation of the Smuggler's Alliance, the return of Garm Bel Iblis, an increase in the organization and size of the New Republic military, the liberation of the beings of Wayland and the Noghri, and a spark of interest in Luke Skywalker to seek out other Force-users that would eventually lead to his creation of the Jedi Praxeum.