The Battle of Long Island, also known as the Battle of Brooklyn and the Battle of Brooklyn Heights, was an action of the American Revolutionary War fought on August 27, 1776, at and near the western edge of Long Island in present-day Brooklyn. The British defeated the Continental Army and gained access to the strategically important Port of New York, which they held for the rest of the war. It was the first major battle to take place after the United States declared its independence on July 4, 1776, in Philadelphia. It was the largest battle of the Revolutionary War in terms of both troop deployment and combat. On August 24, Gen. Sullivan was replaced by Major General Israel Putnam. Unfortunately, he knew little about the terrain of Long Island. Being in charge of the island's defenses, this would come back to haunt the Patriots in the coming battle. Putnam was tasked with overseeing two defensive lines perpendicular to one another. The main line contained about 6,500 troops and were deployed around Brooklyn and faced southeast. This line ran north for 1.5 miles from the mill dam-Gowanus Creek area that emptied into Gowanus Bay to Wallabout Bay. The remaining 3,000 troops were deployed to guard four strategic passes cut by major roads leading to the top and beyond the heights.

Clinton led a crack brigade of light infantry with fixed bayonets in front, followed by Cornwallis who had eight battalions and 14 artillery pieces. Cornwallis was followed by Howe and Hugh Percy with six battalions, more artillery, and baggage. The column consisted of 10,000 men who stretched out over two miles. Three Loyalist farmers led the column toward the Jamaica Pass. The British had left their campfires burning to deceive the Americans into thinking that nothing was happening. The column headed northeast until it reached what later became the village of New Lots, when it headed directly north toward the heights. On September 11, the British received a delegation of Americans consisting of Benjamin Franklin, Edward Rutledge, and John Adams at the Conference House on the southwestern tip of Staten Island (known today as Tottenville) on the former estate of loyalist Christopher Billop. The peace conference failed as the Americans refused to revoke the Declaration of Independence. The terms were formally rejected on September 15. On September 15, after heavily bombarding green Patriot militia forces, the British crossed to Manhattan, landing at Kip's Bay, and routed the Americans there as well. The following day, the two armies battled at Harlem Heights, resulting in a tactical draw. After a further battle at White Plains, Washington retreated across the Hudson to New Jersey. The British occupied New York until 1783, when they evacuated the city as agreed in the Treaty of Paris. The British planned to use Long Island as a staging ground for a new invasion of New England. They attempted to regulate ships going into Long Island Sound and blockaded Connecticut.