[3] He commanded a royalist troop of horse (i.e., cavalry) during the English Civil War, and on the defeat of the king went into exile.

Through the influence of the Duke of York, in 1664 Nicolls was appointed to a commission with Sir Robert Carr (d. 1667), George Cartwright, and Samuel Maverick, to conquer New Netherlands from the Dutch and to regulate the affairs of the New England colonies and settle disputes among them.

Under authority of a commission from the Duke (later King James) Nicolls assumed the position of deputy-governor of New Netherlands (New York).

[5][6][7][8] His policy was vigorous but tactful, and the transition to the new regime was made smoothly and with due regard to the interests of the conquered people.

The formerly Dutch colonists were guaranteed in the possession of their property rights, their laws of inheritance, and the enjoyment of religious freedom.