This prominent position led to conflicts with adjacent port towns. A quarrel arose in 1782 between the inhabitants of Zubarah and Persian-ruled Bahrain. Zubarah natives traveled to Bahrain to buy some wood, but an altercation broke out and in the chaos an Utub sheikh's slave was killed. The Utub and other Arab tribes retaliated on 9 September by plundering and destroying Manama. A battle was also fought on land between the Persians and the Arab tribes, in which both sides suffered casualties. The Zubarans returned to the mainland after three days with a seized Persian gallivat that had been used to collect annual treaty. On 1 October, 1782, Ali Murad Khan ordered the sheikh of Bahrain to prepare a counter-attack against Zubarah and sent him reinforcements from the Persian mainland. About 2,000 Persian troops arrived in Bahrain by December 1782; they then attacked Zubarah on 17 May 1783. After suffering a defeat, the Persians withdrew their arms and retreated to their ships. An Utub naval fleet from Kuwait arrived in Bahrain the same day and set Manama ablaze. The Persian forces returned to the mainland to recruit troops for another attack, but their garrisons in Bahrain were ultimately overrun by the Utub. It is well known that the strategist of this battle was Shaikh Nasr Al-Madhkur, his sword fell into the hands of Salama Bin Saif Al Bin Ali after his army collapsed and his forces were defeated. The Alkhalifa conquered and expelled the Persians from Bahrain after defeating them. After the invasion, the Al Khalifa migrated to Bahrain, with Zubarah remaining under their jurisdiction. The Bani Utbah was already present at Bahrain at that time, settling there during summer season and purchasing date palm gardens. Despite the instability surrounding Zubarah after the siege of Zubarah and the conquest of Bahrain in 1783, it flourished as a trading centre and its port grew to be larger than that of Qatif's by 1790. Al Zubarah developed into a center of Islamic education during this century. The town came under threat from 1780 onward due to the intermittent raids launched by the Wahhabi on the Bani Khalid strongholds in nearby al-Hasa. The Wahhabi speculated that the population of Zubarah would conspire against the regime in Al-Hasa with the help of the Bani Khalid. They also believed that its residents practiced teachings contrary to the Wahhabi doctrine, and regarded the town as an important gateway to the Persian Gulf.