Fantasy Lord: Start with Daily Intelligence

The protagonist ambushed two mountains in the lower reaches of the Maine River Valley. The dam was filled with water. It was flood season again. The magic crystal cannon ignited the fierce oil, which restricted 4,000 ordinary minotaurs in place. Eleven second-level minotaurs rushed up, and then Lajos Assad opened the dam, which washed away 4,000 minotaurs. The remaining eleven second-level minotaurs were surrounded and killed on the mountain by the eight great knights, more than 70 formal knights, 300 apprentice knights, and thousands of reserve knights of the Maine River Valley.

As for the flood that did not hit the protagonist's men, the reason was very simple. They were on the mountain!