What is the main topic of this passage?

Today I’d like to continue our discussions of American diplomatic history in 18th century by talking about a pioneer named William Johnson. Sir William Johnson helped to establish friendly relations between the British colonies and Iroquois nation during the middle of the 18th century. Johnson came to New York state from Eng land in 1737, and soon became a large land holder. He got along well with Iroquois. Some of them lived on his land, and it became the center of trade. Johnson sought land and furs, but was generous to his neighbors. With his skill of diplomacy, Johnson often spent his time negotiating among various Indian groups. Largely because of his work, the Iroquois aided the British in their struggles against the French in 1757. Later, however, there was a disagreement with the Iroquois. Johnson, who had been an official in the colonial government, was called in to conclude a treaty regarding land boundaries between the Iroquois and the English settlers in the area. Since Johnson died in 1774, he didn’t have to face the turmoil of the American Revolution.