When Khalid ibn Walid leaves from Ain-ul-Tamr to Daumat ul jandal for the help of Ayadh, the Persian court believes that Khalid had returned to Arabia with a large part of his army.
The Persians decide o throw the Muslims back into the desert and regain the territories and the prestige which the Persian Empire had lost.
The Persians had resolved not to fight Khalid again, but they are quite prepared to fight the Muslims without Khalid ibn al-Walid.
