The plan partially worked

During the Y'All war about 12,000 years ago the brunt of the fighting was done by Ult and Wurgus with virtually no Kermac ships participating.

The Wurgus lured a large part of the Y'All Invasion Fleet into their solar system and then ignited their own sun in a Supernova Explosion. Back then Wurgus Sun manipulating technology was very limited compared to the technology they have available now. The Wurgus lost their home system but managed to destroy 1/3rd of the Y’All fleet.

At that time the Y'All turned and left. Until the Y'All returned several thousand years later the plan was considered to have worked.

Classified - Narth Independently of the Wurgus plan, a single Narth Sphere destroyed hundreds of thousands of Y'All ships, with the total coming close to the number destroyed by the Wurgus Super Nova. Together the two events accounted for over 80% of the Y'All ships destroyed.