See H. L. Osgood, The American Colonies in the Seventeenth Century (3 vol., 1904-7, repr. 1957).
The United Colonies of New England, commonly known as the New England Confederation, was a political and military alliance of the British colonies of Massachusetts, Plymouth, Connecticut, and New Haven. Established May 19, 1643, its primary purpose was to unite the Puritan colonies against the Indians. It was established as a direct result of a war which started between the Mohegan and Narragansetts. It also provided for the return of fugitive criminals and indentured servants, and served as a forum for resolving inter-colonial disputes.
The confederation was weakened in 1654 after Massachusetts refused to join the war against the Netherlands during the First Anglo-Dutch War, however the confederation regained importance during King Philip's War in 1676.
The New England Confederation was highly successful in terms of bonding the colonies together, and provided a basis for the further collaboration of Colonies in times such as the American Revolution.
The colonies united for defense purposes — they wanted to protect themselves from the Indians, the French, and the Dutch. In the New England Confederation, each colony had two votes regardless of population.
The New England Confederation excluded Rhode Island, as Rhode Island was thought of as anarchistic, sometimes being called "Rogue Island". Rhode Island was also more sympathetic to Native Americans.