Why did the Iroquois ally themselves with Britain?

Answer 1

In the Revolutionary War Period of America's history, the Iroquois generally favored alliances with Great Britain rather than the American colonists for one fundamental reason: the British were less of a threat than the colonists were, which is to say that they had more to gain from helping the British than helping the nascent "Americans." The British cannily garnered Iroquois support by also supplying them with arms and other helpful resources.

Answer 2

During the French and Indian war, the French had a number of Indian tribes fighting on their side. The British wanted an alliance with the Iroquois because they would rather have them fighting the French and other Indian tribes than fighting their own solders. Neutrality by Indian tribes was almost impossible.