The Battle of Trenton was a small but pivotal American Revolutionary War battle on the morning of December 26, 1776, in Trenton, New Jersey. After General George Washington's crossing of the Delaware River north of Trenton the previous night, Washington led the main body of the Continental Army against Hessian auxiliaries garrisoned at Trenton. After a brief battle, almost two-thirds of the Hessian force were captured, with negligible losses to the Americans. The battle significantly boosted the Continental Army's waning morale, and inspired re-enlistments.

The Continental Army had previously suffered several defeats in New York and had been forced to retreat through New Jersey to Pennsylvania. Morale in the army was low; to end the year on a positive note, George Washington, Commander-in-Chief of the Continental Army, devised a plan to cross the Delaware River on the night of December 25–26 and surround the Hessians' garrison.

Because the river was icy and the weather severe, the crossing proved dangerous. Two detachments were unable to cross the river, leaving Washington with only 2,400 men under his command in the assault, 3,000 fewer than planned. The army marched 9 mi (14.5 km) south to Trenton. The Hessians had lowered their guard, thinking they were safe from the Americans' army, and had no long-distance outposts or patrols. Washington's forces caught them off guard, and after a short but fierce resistance, most of the Hessians surrendered and were captured, with just over a third escaping across Assunpink Creek.

Despite the battle's small numbers, the victory inspired patriots and sympathizers of the newly formed United States. With the success of the ongoing revolution in doubt a week earlier, the army had seemed on the verge of collapse. The dramatic victory inspired soldiers to believe the war was not a lost cause and serve longer. It also attracted new recruits to the ranks.

In early December 1776, American morale was very low. The Americans had been ousted from New York by the British and their Hessian auxiliaries, and the Continental Army was forced to retreat across New Jersey. Ninety percent of the Continental Army soldiers who had served at Long Island were gone. Men had deserted, feeling that the cause for independence was lost. Washington, Commander-in-Chief of the Continental Army, expressed some doubts, writing to his cousin in Virginia, "I think the game is pretty near up."

At the time a small town in New Jersey, Trenton was occupied by four regiments of Hessian soldiers (numbering about 1,400 men) commanded by Colonel Johann Rall. Washington's force comprised 2,400 men, with infantry divisions commanded by Major Generals Nathanael Greene and John Sullivan, and artillery under the direction of Brigadier General Henry Knox.

George Washington had stationed a spy named John Honeyman, posing as a Tory, in Trenton. Honeyman had served with Major General James Wolfe in Quebec at the Battle of the Plains of Abraham on September 13, 1759, and had no trouble establishing his credentials as a Tory. Honeyman was a butcher and bartender, who traded with the British and Hessians. This enabled him to gather intelligence and to convince the Hessians that the Continental Army was in such a low state of morale that they would not attack Trenton. Shortly before Christmas, he arranged to be captured by the Continental Army, who had orders to bring him to Washington unharmed. After being questioned by Washington, he was imprisoned in a hut to be tried as a Tory in the morning, but a small fire broke out nearby, enabling him to "escape". On the evening before the battle, Hessian commander Rall was celebrating Christmas with his troops at the farm of Abraham Hunt, a wealthy merchant and farmer of Trenton. Hunt played the role of a friendly Loyalist host, giving Rall a false sense of serenity while Washington and his troops were preparing for a surprise attack.

The U.S. plan relied on launching coordinated attacks from three directions. General John Cadwalader would launch a diversionary attack against the British garrison at Bordentown, New Jersey, to block off reinforcements from the south. General James Ewing would take 700 militia across the river at Trenton Ferry, seize the bridge over the Assunpink Creek and prevent enemy troops from escaping. The main assault force of 2,400 men would cross the river 9 mi (14 km) north of Trenton and split into two groups, one under Greene and one under Sullivan, to launch a pre-dawn attack. Sullivan would attack the town from the south, and Greene from the north. Depending on the success of the operation, the Americans would possibly follow up with separate attacks on Princeton and New Brunswick.