Raid on Ilum

Several years after the Treaty of Coruscant began the Cold War in 3653 BBY, the Sith Empire sent a small group of Sith to the Jedi Order's holy world of Ilum to investigate the planet's reserves of potentially valuable Adegan crystals. The Sith managed to avoid the few Jedi on Ilum, leaving the Jedi largely unaware of their presence as the strike team began to quietly harvest crystals.

However, in 3640 BBY, the Empire's scientists discovered that Adegan crystals could be used in the development of stealth technology, and they launched an invasion of the planet to take advantage of the crystal deposits.

Text and facts from the “Raid on Ilum” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.