As the Later Zhao collapsed under the weight of civil war in 350, Duan Kan led his followers south and occupied Chenliu Commandery (陳留郡; around present-day Kaifeng, Henan).
While Shandong's natural terrain offered them a robust defense, it appears that they did not, or were unable to, make any real effort to expand.
In 351, Duan Kan became a vassal to Jin, who appointed him the General Who Guards the North and demoted his title to Duke of Qi.
His brother, Duan Qin (段欽) was captured while his officials, Yuan Fan (袁范), Pilu Yu (辟閭蔚) and others were killed.
While Duan Kan held on to Guanggu, Murong Ke built forts and cultivated land to prepare for a long siege.
Jin sent the general, Xun Xian to help him, but fearful of the Yan army's strength, he stopped his advance once he reached Langya Commandery.
Desperately, Duan Kan mustered his remaining troops and once again led them out to give battle, but was defeated within the Yan encirclement.
Despite his initial leniency, for unknown reasons, Murong Jun had Duan Kan killed, first poisoning his eyes, and buried alive 3,000 of his followers in 357.