Muslim Arab opposition to the Crusaders, initially fragmented among various petty states, begins, after 1128, gradually to unify under the strong leadership of the Turkish Zangid dynasty, which from 1127 to 1222 is to rule northern Iraq (al-Jazirah) and Syria.

Mahmud II rewards the loyal Zengi with the governorship of Mosul in 1127 following the failed rebellion of Caliph al-Mustarshid.

The key city of Aleppo submits to Zengi's authority to secure military protection against a possible Frankish crusader conquest.

Bohemond’s rule will be marked from 1128 by conflicts with Joscelin I of Edessa and skirmishes in the northern border.

Both Bohemond and Joscelin attack Aleppo individually, but refuse to cooperate in a larger siege against the city.

Roger of Salerno had given away territory to Joscelin, but Bohemond does not consider these donations legitimate as they had been made without his authority, even though he had been a minor at the time.

The dispute comes to open conflict between Antioch and Edessa, with Joscelin allying with the Muslims against Bohemond.

The Latin Patriarch of Antioch places an interdict over the County of Edessa.

Bohemond’s cousin Roger II invades and conquers Taranto in 1128, claiming it as the heir of William II of Apulia.

Bohemond, being away, can do nothing to prevent this.

This year, Baldwin II marches north to mediate in the dispute, and Joscelin abandons his claims.

Meanwhile, the atabeg Zengi consolidates his power over Aleppo and Mosul and the crusaders will never again have a chance to impose their authority over Aleppo.

Baldwin plans to attack Aleppo as well, but Antioch, which had passed to Bohemond II when he came of age in 1126, had begun to fight with Edessa and the plan fell through.

Aleppo and Mosul are united under the much stronger ruler Zengi in 1128, and Crusader control of northern Syria begins to dwindle.

Zengi, atabeg of Aleppo and Mosul, had allied with Taj al-Mulk Buri of Damascus against the crusaders in 1130, but this had been only a ruse to extend his power; he had had Buri's son taken prisoner and seized Hama from him.

Zengi had also besieged Homs, the governor of which had been accompanying him at the time, but could not capture it, so he returned to Mosul, where Buri's son and the other prisoners from Damascus had been ransomed for fifty thousand dinars.

Zengi had agreed in 1131 yo return the fifty thousand dinars if Buri would deliver to him Dubays ibn Sadaqa, emir of al-Hilla in Iraq, who had fled to Damascus to escape al-Mustarshid.

When an ambassador from the caliph arrived to bring Dubais back, Zengi had attacked him and killed some of his retinue; the ambassador had returned to Baghdad without Dubais.

Baarin, a village in northern Syria, serves in the early twelfth century as a fortress of the Crusaders, who refer to it as "Mons Ferrandus" or "Montferrand."

In 1133, Pons of Tripoli escapes to Baarin for refuge where, according to chronicler William of Tyre, he is shortly besieged by the Muslim army of Aleppo led by Zengi before being rescued by King Fulk of Jerusalem.

A civil war had broken out in the Seljuq western territories at the death of sultan Mahmud II in 1131.

Zengi had been recalled to the East by certain rebel members, stimulated by the Caliph and Dubais.

Defeated, Zengi had fled.

The Caliph al-Mustarshid had pursued him to Mosul, and besieged him there but without success for three months.

It had nonetheless been a milestone in the revival of the military power of the caliphate.

Zengi now resumes operations in Syria and in 1134 lays siege to Damascus, but is induced, partly by the bravery of the enemy, partly at the instance of the Caliph, to whom Zengi had made some concession in the public prayers, to relinquish the attempt.

Recalled again by troubles in the East, he will be unable to do much against the Crusaders until after al-Mustarshid's death.

Zengi had became involved in Artuqid affairs in 1134, allying with the emir Timurtash (son of Ilghazi) against Timurtash's cousin Da'ud.

Zengi's real desires, however, lie to the south, in Damascus.

In 1135.

Zengi receives an appeal for help from Ismail, who had succeeded his father Buri as emir of Damascus, and who is in fear for his life from his own citizenry, who consider him a cruel tyrant.

Ismail is willing to surrender the city to Zengi in order to restore peace.

None of Ismail's family or advisors want this, however, and Ismail is murdered by his own mother, Zumurrud, to prevent him from turning over the city to Zengi's control.

Ismail is succeeded by his brother Shahib ad-Din Mahmud.

Not discouraged by this turn of events, Zengi arrives at Damascus anyway, still intending to seize it.

The siege lasts for some time with no success on Zengi's part, so a truce is made and Shahib ad-Din's brother Bahram-Shah is given as a hostage.

At the same time, news of the siege had reached the caliph and Baghdad, and a messenger is sent with orders for Zengi to leave Damascus and take control of the governance of Iraq.

The messenger is ignored, but Zengi abandons the siege, as per the terms of the truce with Shahib ad-Din.

On his way back to Aleppo, Zengi besieges Homs, whose governor had angered him.

Shahib ad-Dini responds to the city's call for help by sending Mu'in ad-Din Unur to govern it.