This war was a conflict fought in another galaxy between two droid species, the Silentium and Abominor.
Eons ago, a species of star-shaped organics created the Silentium to resemble their form, in much the same way that humanoid sentients created bipedal droids. Though the organics were wiped out by a radiation storm from a nearby supernova, their droid creations lived on. These droids continued to reproduce and improve themselves, and developed a culture based on the prime numbers of five, seven, and eleven.
An Abominor
Many of them took on the form of geometric shapes, with the circle being the "holiest" of shapes. Thousands of the wisest members of the droid race created powerful fifty-kilometer spheroid bodies. Two influential members of this giant variety included The One and The Other, and the others were collectively called The Rest. However, this culture of order and symmetry was soon challenged by the chaotic Abominor, self-constructing droids with a lust for power.
The two sides fought a galactic war until the Yuuzhan Vong, one of the galaxy's native organic species, rose up and forced the droid species to flee.
The war between the Silentum and the Abominor is strongly implied to be the root cause of the technophobia of the Yuuzhan Vong. It was later confirmed in the blog post The Droids Re-Animated.
- The New Essential Guide to Droids