By 641, the Muslims had captured most of the Southwestern part of the Persian Empire.
This area contained the best and most fertile lands and would be modern-day Iraq, Kuwait, and parts of northwestern Iran.
As mentioned previously, Umar had grown weary of all the fighting and was grateful for their current holdings.
However, the Persian pride was wounded and they couldn't accept a peace treaty with the Muslims.
Emperor Yesdijird made his base in Nihavan and began to build another army to attack the Muslims.