Sudden clash

This proverb accurately describes the essential factors of warfare.

Timing, geography, and people to win the war.

Evidently, the Dark Lord's side was well prepared for this fight. Hence, they had spent quite some efforts in choosing the location of battle.

The elves were presently trapped along a bare mountain path near the peak. Even without rain, the land here was pretty barren. Harsh winds swept through the area and falling off the precipitous cliff would mean certain death. It was extremely difficult to escape.

The forces of darkness naturally occupied the terrain advantage.

Furthermore, the barren land here meant that the favored children of nature, the elves, were considerably weakened when fighting in this terrain.