Usama went to Homs, where he was taken captive in a battle against
Zengi, the
atabeg of
Mosul and
Aleppo, who had just captured nearby Hama. After his capture he entered Zengi's service, and travelled throughout northern Syria, Iraq, and Armenia fighting against Zengi's enemies, including the
Abbasid caliph outside
Baghdad in 1132. In 1135, he returned to the south, to Hama, where one of Zengi's generals, al-Yaghisiyani, was appointed governor. He returned to Shaizar when his father died in May 1137, and again in April 1138 when
Byzantine emperor John II Comnenus besieged the city. The emperor's siege of Shaizar was unsuccessful, but Shaizar was heavily damaged. After the siege, Usama left Zengi's service and went to
Damascus, which was ruled by
Mu'in ad-Din Unur, the atabeg of the
Burid dynasty. Zengi was determined to conquer Damascus, so Usama and Unur turned to the crusader
Kingdom of Jerusalem for help. Usama was sent on a preliminary visit to Jerusalem in 1138, and in 1139 Zengi captured
Baalbek in Damascene territory. In 1140, Unur sent Usama back to Jerusalem to conclude a treaty with the crusaders, and both he and Unur visited their new allies numerous times between 1140 and 1143. During these diplomatic missions Usama developed a friendship with members of the
Knights Templar whom he considered more civilized than other crusader orders. Afterwards, Usama was suspected of being involved in a plot against Unur, and he fled Damascus for
Fatimid Cairo in November 1144. In Cairo he became a wealthy courtier, but he was involved in plots and conspiracies there as well. The young
az-Zafir became caliph in 1149, and
Ibn as-Sallar became
vizier, with Usama as one of his advisors. As-Sallar sent Usama to negotiate an alliance against the crusaders with Zengi's son
Nur ad-Din, but the negotiations failed. Usama took part in battles with the crusaders outside of
Ascalon on his way back to Egypt, and after he left, his brother 'Ali was killed at
Gaza. Back in Egypt, as-Sallar was assassinated in 1153 by his son Abbas, Abbas's son Nasr, and caliph az-Zafir, who, according to Usama, was Nasr's lover. Thirteenth-century historian
Ibn al-Athir says that Usama was the instigator of this plot. Usama may also have been behind the assassination of az-Zafir by Abbas, in 1154. Az-Zafir's relatives called upon a supporter,
Tala'i ibn Ruzzik, who chased Abbas out of Cairo, and Usama followed him. He lost his possessions in Cairo, and on the way to Damascus his retinue was attacked by the crusaders and
Bedouin nomads, but in June 1154 he safely reached Damascus, which had recently been captured by Nur ad-Din. Ibn Ruzzik tried to persuade him to come back, as the rest of his family was still in Cairo, but Usama was able to bring them to Damascus, through crusader territory, in 1156. The crusaders promised to transport them safely, but they were attacked and pillaged, and Usama lost his entire library. == Later years ==