Muhammad was very distantly related to the founder of the Saffarid amirate, Ya'qub-i Laith Saffari; his great-great-grandfather had been the brother of Ya’qub's great-grandfather.

Taking advantage of his ties to the Saffarids, Abu Ja’far Ahmad gained the support of the city ‘ayyars, who stopped an attempt by ‘Abdallah's son ‘Aziz to maintain control of the town.

Abu Ja’far Ahmad's rule soon expanded outside Zarang; ‘Abdallah's representative in al-Rukhkhaj defected to him and the citizens of Bust threw their support behind the Saffarid as well.

Having successfully defended against the rebels, Abu Ja’far Ahmad sought to expand his realm at the expense of the Abbasid Caliphate, which had been suffering a series of setbacks over the last several years.

Because he was frequently needed in Bust and other parts of the eastern provinces, Abu Ja’far Ahmad often left Zarang in the hands of the three sons of one Tahir b. Asnam.

After these initial troubles, Sistan and the outlying provinces calmed down for several years, making for a relatively peaceful period in Abu Ja’far Ahmad's reign.

In the meantime, the three sons of Tahir b. Asnam who sometimes governed in Abu Ja’far Ahmad's name when he was absent from Zarang fell from favor and were imprisoned.

The amir's son and heir, Abu Ahmad Khalaf, happened to outside of the capital the night of the murder and less than two months later managed to establish himself in Zarang.