The exact reasons for the conflicts are not known although the history between the two races was said to be complicated. Much of the information on this period in the history of both cultures was unreliable since both sides made heavy use of propaganda, and even 300 years later many people of both species continued to despise each other. Denobulans demonised Antarans and turned them into a faceless enemy, while Antarans were taught from childhood that every Denobulan was an enemy.
During the conflict, at least according to propaganda, Denobulan battle tactics resulted in 20 million Antaran casualties and Denobulan doctors experimented on Antarans. After the last war neither side tried to reconcile, and the two races severed all relations to the extent that when the Antaran Hudak met the Denobulan Phlox in 2153, Hudak claimed to be the first Antaran in six generations to see a Denobulan. By that time, members of both races still hated each other, even though many Denobulans had put it behind them and grown more open-minded. (ENT: "The Breach")