The New Separatist Crisis was a war that occurred between the New Republic and the Separatist Alliance in 8 ABY, ending in 10 ABY. The Separatist Alliance emerged victorious, destroying the New Republic and sending it's leaders into exile in the Unknown Regions. The war saw massive armies take arms and fight on a galactic scale. Immense casualties were taken by both sides, by the New Republic's organic soldiers and the Alliance's droids.
After the war, the galaxy became under the control of the Separatist Alliance for many years. In 130 ABY, the Sith Lord Darth Krayt took over the Separatist Alliance by a military coup and reformed it into the new Sith Empire.