Introduction:
The Il-Khans were a Persian-Mongol dynasty that ruled over a large part of the Middle East from the 13th to the 14th century. They were initially followers of the Mongolian traditional religion, but over time, many of their rulers converted to Islam. Among these rulers, the first Il-Khan to convert to Islam was Ghazan Khan.

Explanation:
Ghazan Khan was the seventh ruler of the Il-Khanate, reigning from 1295 to 1304. He was born as Mahmud Ghazan, the son of Arghun Khan, who was a Buddhist. However, when Ghazan Khan came to power, he decided to convert to Islam, specifically to the Sunni branch of Islam.

Reasons for Conversion:
There were several factors that influenced Ghazan Khan's decision to convert to Islam:

1. Political Consolidation: Ghazan Khan's conversion to Islam helped him gain the support of the Muslim majority in his empire. This was particularly important as the Il-Khans ruled over a predominantly Muslim population.

2. Economic Stability: Ghazan Khan believed that converting to Islam would help stabilize the economy of his empire. Islamic law, known as Sharia, provided a framework for economic activities that he believed would benefit his subjects.

3. International Relations: Ghazan Khan aimed to improve diplomatic relations with other Muslim states, such as the Mamluks of Egypt and the Sultanate of Delhi. By converting to Islam, he hoped to strengthen political and economic ties with these states.

4. Mongol Tradition: Despite converting to Islam, Ghazan Khan still maintained certain Mongol traditions and practices. This allowed him to strike a balance between his Mongol heritage and his new religious affiliation.

5. Personal Conviction: Although political and strategic considerations played a significant role in his decision, Ghazan Khan was also personally convinced of the merits of Islam. He became a devout Muslim and actively promoted the religion throughout his empire.

Conclusion:
Ghazan Khan's conversion to Islam marked a significant turning point in the history of the Il-Khanate. His decision had far-reaching implications for the empire's political, economic, and cultural landscape. It set the stage for subsequent Il-Khan rulers to embrace Islam and established a lasting Islamic legacy in the region.