Given the attitudes of the Terrills how did the Hannassey's survive?

The Hannasseys rough up Pat's fiancé a bit and that was enough for a whole army of men to ride on the Hannassey's property, rouse and threaten the women folk and ruin the water supply. Then they go into town and find some men and beat them significantly.

Seems that a full fledged war would have happened long before our story begins and the Terrill's with superior man power would have ruined the Hannasseys.