Battle of Eredenn

The Battle of Eredenn occurred when Separatist General Sev'rance Tann arrived at the planet during the Hunt for the Decimator after learning of the weapon's existence from Boorka the Hutt.

The battle
At Count Dooku's command, Tann's army quickly exterminated the clone trooper garrison there and captured the research facilities that were working on the Decimators. The Wookiee's support of the Eredenn Prime army arrived too late to save the clones and the CIS killed half of the support But not Without The Activation codes Being stolen by some clones that with a fortune escaped from the massacre thanks for the Distraction of the Wookiees. The rest escaped to Alaris Prime With the codes to help the clans of Wookiee stationed along with the clone army.

Aftermath
She retrieved the machines and took a protocol droid that had data on the Decimator. Sev'rance Tann had thus gotten one step closer to having the Decimator under her control.

Source

 * Star Wars: Galactic Battlegrounds: Clone Campaigns
 * The Complete Star Wars Encyclopedia