From the Smithsonian - the National Museum of the American Indian

The assembly of the Wampanoag Peoples and the English settlers in 1621 had much more to do with political alliances, diplomacy, and a pursuit of peace. 

The Wampanoag Peoples had a long political history dealing with other Native Nations before the English arrived. The Wampanoag shared their land, food, and knowledge of the environment with the English. Without help from the Wampanoag, the English would not have had the successful harvest that led to the First Thanksgiving. 

However, cooperation was short lived, as the English continued to attack and encroach upon Wampanoag lands in spite of their agreements. Interactions with Europeans and Americans brought accelerated and often devastating changes to American Indian cultures. 

As with all lessons that discuss Native American culture and history, it is important to include accurate details, be tribally specific, and practice cultural sensitivity when teaching about Thanksgiving. Just as they were before the English arrived, Native Americans like the Wampanoag Peoples are dynamic and active participants in all aspects of society.