Part 8/10:
Another significant factor was his fear of Aragorn's sword, Andúril. This weapon, re-forged from the remnants of Narsil, held magical properties that had previously caused Sauron significant harm. The fear of being wounded again by a sword with such a storied history kept Sauron at bay.
However, the most pressing reason was the overwhelming advantage he held in numbers. He had a colossal army, estimated to be ten times larger than that of the free peoples of Middle-earth. Sauron, confident in his impending victory, saw no reason to risk himself in battle. His assumption that nobody could challenge his power played into his decision not to act directly.