Dhaher, similar to many other strong local leaders under the Ottoman Empire who did not owe their power to the central Ottoman authorities, was disliked by the Ottoman administration. The Ottoman Sultan sent an order to the governor of Damascus, Sulayman Pasha Al Azem, to put an end to Dhaher's rule in the Galilee. In September 1742, a military force led by the governor of Damascus came to the Galilee and laid siege to Tiberias. 83 days later, the siege was lifted due to the departure of the Hajj pilgrimage caravan. In July 1743 the governor returned with a larger force. A month later the governor died of kidney disease and the siege was lifted for good.
After the threat from the Ottoman administration was removed, Dhaher again expanded his realm. Dhaher turned west and took control over surviving Crusader fortresses. Acre was taken over and fortified by Dhaher, and became the main city of the area he governed. When Haifa was conquered by Dhaher, its location wasn't considered defensible, so that the city was razed and rebuilt at a new location 3 km away, with improved fortifications and a new seaport. Now controlling the major seaports in the area, Dhaher made contact with Maltese pirates. Dhaher and the pirates agreed to barter the stolen goods they took — the pirates from different ships they looted, and Dhaher from his looting of travelers to Damascus and Mecca.
Dhaher (unlike many governors and rulers in the middle east at the time) was very aware of the importance of a flourishing economy to provide a stable basis for his rule — he tried to refrain from squeezing the peasants with extortionately excessive taxes, and established a state monopoly on cotton-growing in the Galilee. The city of Acre underwent an economic boom (partly based on its role in exporting cotton grown in the Galilee to France).
In 1768, the central Ottoman authorities partially recognized or legitimized his de facto position by granting him the title of "Sheikh of Acre, Amir of Nazareth, Tiberias, Safed, and Sheikh of all Galilee".
From 1769 to 1775, Dhaher got involved in a war that led to his downfall. In 1750, his friend Ali Bey Al-Kabir was appointed the governor of Egypt and soon got into an argument with the Ottoman administration. Assassins were sent to kill Ali Bey, for fear of him attempting to rebel against the Ottoman Empire (1769). In response, Ali Bey declared Egypt to be an independent country. Dhaher helped Ali Bey by blocking an Ottoman force heading south to suppress the rebellion in Egypt. Bey sent a force of 30,000 which conquered most of Palestine and Damascus from November 1770 to June 1771. After the troops arrived at Damascus (with help from Dhaher) in 1771, the commander of the troops, Abu al-Dhahab, refused to continue fighting against the Ottomans, and turned against Ali Bey. When these troops returned to Egypt, Ali Bey fled to Acre to shelter under Dhaher's protection. The combined forces of Dhaher, Ali Bey, and Russia (which was at war with the Ottoman Empire that time) kept the majority of the Galilee free of Ottoman influence, and Dhaher was able to temporarily extend his rule along the coast as far south as Jaffa and as far north as Sidon. In 1773 Ali Bey returned to Egypt, but was defeated by the rebels against his authority and died. In 1774, the war between Russia and the Ottomans came to an end, and Dhaher was left without any outside support.
Historically, his family was linked to the Qaissite party to which belonged the governors of Mount Lebanon, the Maans (1518 - 1697) and the Shihabs (1697 - 1842) whose territory included the Galilee. As allies of those powerful governors, members of Dhaher's family had been appointed sheiks of some parts of the Galilee since 1518. The autonomy achieved by the governors of Mount Lebanon played an important role in forming the political views of Dhaher al-Omar.
Through marriage, he sealed the alliances with the Bedouin sheikhs and the prominent notables of Galilee. He encouraged Jewish families to settle in Tiberias around 1742. The newcomers helped him with the influence of their network in Damascus and Istanbul. Also, Dhaher maintained excellent relationships with the Greek Orthodox church in Nazareth and Acre which secured for him the sympathy and support of Russia. Dhaher understood early on the importance of a multi-confessional society as a means of prosperity and political support.
Constantin-François Volney, who wrote the first European biography of Dhaher in 1787, lists three main reasons for Dhaher´s failure. First, the lack of "internal good order and justness of principle". Secondly, the early concessions he made to his children. Third, and most of all, the avarice of his advisor and confidant, Ibrahim Sabbar.