When arab armies conquered iran, it was known as

The correct answer is: Persia

Explanation:

The Arab conquer of Iran, Better known as the Muslim conquest of Persia was an event that resulted in the fall of the Persian Empire in 651 A.D. In this years what we know nowadays as Iran was part of the Big Persian empire of the VI century. The Persian fall was due to The Muslims taking advantage of their growth and that the Persian Empire of that time the Sasanian Empire, was known as the weaker reign of the Persian Empire.

This Muslim conquest started in 633 with the first Arab invasion of Mesopotamia, invasions that succeded, and in 636 Mesopotamia was in Muslim control, after this the Muslim campaign grew and Battles like the Battle of Nahvad in 642 inspired them to try and finish the weakened Persian empire by dominating the Center first and then plan the strategy from there, and finally in 651 the Muslims were able to control The Sasanian Empire and with it Armenia, Azerbaijan and Khorasan, all in Persian control.