Tahir spent much of his time early in his reign in the western part of his territories, having to deal with the occupation of Fars by the Abbasid Caliph al-Mu'tadid after the downfall of 'Amr.

A second campaign resulted in a caliphal grant of the province to Tahir, although both Fars and Kerman effectively fell into the hands of Sebük-eri.

Over the next few years the two brothers began to lose the confidence of the people, and although the government bureaucracy continued to function, the stability of the provinces declined as rival factions opposed each other.

Despite reinforcements from Sebük-eri, however, he was unable to dislodge al-Laith and began to suffer from having very little money to maintain the support of those around him, thanks to declining government revenues.

The two sides met in June 909; Sebük-eri, who had managed to win over Tahir's commanders, won an easy victory and captured the brothers.