Early in 1776, Charles Lee had begun fortifying the city of New York. He did not believe the city could be held against a protracted British assault. Located on the southern tip of Manhattan Island, the city was vulnerable to British seapower. Despite this strategic weakness, New York was too important economically and politically to be surrendered without a fight. As a thriving port with excellent harbors, it would give the British an invaluable base for military operations. It provided access to the Hudson River and the chain of waterways that acted as a highway and invasion route to and from Canada. British control of the Hudson River Valley would threaten overland communication between New England and the rest of the United States. Congress was determined to defend the city. Once Boston was secure, Washington began moving his army to New York.

Washington was convinced that New York, a place of “infinite importance,” could be kept from the enemy. He threw himself into the work of organizing its defenses. He eventually assembled a force that on paper numbered around 30,000, though two-thirds of these were militia and many who were on the rolls were not actually present and ready for service. The Americans continued the construction of fortifications on Manhattan. Washington ordered more fortifications to be built on Long Island, around the village of Brooklyn, which lay just across the East River from New York. The main American position was on Brooklyn Heights, which rose 100 feet above the surrounding ground. A number of gun emplacements were built along the North and East Rivers, to prevent British ships from passing up them and separating the Americans on the islands from each other or from the mainland.

Washington garrisoned Manhattan and Long Island and then awaited the British attack. In doing so, he left his army open to complete destruction. He had divided his force between two islands in the face of a numerically superior enemy who had command of the sea. The British navy soon demonstrated that it could cut Washington's forces off at will by sailing some ships up and down the North River, past the ineffectual American batteries. Despite this, Washington and his army stayed in place. They remained confident. Their only experience of war had been the siege of Boston, where the British had impaled themselves on Bunker Hill. Amateurs at war, they thought the enemy would act according to expectation.

On July 2, General Howe landed a force of 9,300 men on Staten Island.

This became his base of operations. Howe's intentions in the New York campaign were initially what the Americans feared. He wanted New York as a launching point for operations up the Hudson to cooperate with forces from Canada. He also intended to use it as a convenient place from which to launch attacks on New England. In a letter to Lord Germain, Howe expressed his desire for a decisive battle that would destroy the American army and crush the spirit of resistance in the colonies.

The arrival of his brother Lord Howe brought a diplomatic interlude. The Howes had been appointed peace commissioners. Unfortunately, all they could offer the Americans was pardon for a prompt submission to royal authority. Abortive communications with the rebels went nowhere. In the meantime, General Howe's plan of campaign was shifting. When the last of his troops arrived, the campaigning season was well advanced. He was impressed by the number of American defenders in New York and their fortifications. Perhaps he was influenced by his brother, who hoped a display of British military superiority would bring the Americans to their senses without much bloodshed. When it came time to fight, Howe moved at a leisurely pace and passed up opportunities to destroy Washington's army, preferring to wage a war of maneuver aimed at capturing territory with a minimum of casualties.