Washington had been humiliated in New York.  He had botched the defense of the city and been forced to flee with his army north along the Hudson with the British close on his heels.  He tried to slow their advance (and redeem his reputation) by strengthening the garrisons at Fort Washington and Fort Lee, but the British took both forts—Washington on 16 November and Lee on 19 November.  

Washington next fled north to Peekskill, then crossed the Hudson and double-backed to the south toward the Delaware River. British Generals Cornwallis and Howe followed in hot pursuit.  Cornwallis could have caught Washington’s retreating army at New Brunswick, but Howe (typically) ordered Cornwallis to slow his advance. This enabled Washington to reach Trenton, New Jersey on 7 December and cross the Pennsylvania River into Pennsylvania.  

At this point, Washington got clever; he made sure to use every boat within miles.  When Howe reached Trenton the following day, he had no way to cross. For a week he scoured the New Jersey shore for boats.  But finding none, he ordered his army into winter camp.  Small garrisons were left at Trenton, Princeton, and Bordertown, but the majority of Howe’s army was quartered in New York.

Washington could have sat safe for the winter.  But several considerations urged him toward action.  Almost half of his 3000-man army was enlisted only through the end of the year; they would soon be going home.  The other half suffered from sagging morale.  And according to his intelligence, the Hessian troops stationed across the river in Trenton had taken few measures to fortify their position.  Therefore, on 25 December, Washington led 2400 men across the icy river and took the sleepy and Christmas cheer-filled garrison by surprise.  After less than an hour of fighting, the Hessians surrendered.  Only two Americans were killed; more than 900 Hessian mercenaries were taken prisoner.

Washington returned to his camp on the other side of the Delaware River; but believing that he could take another British winter camp, he re-crossed the Delaware on 31 December and occupied Trenton.  Meanwhile, Cornwallis, who had broken camp after hearing of Washington’s Christmas surprise, marched an army of 6000 men toward the Delaware.  When he pulled into Trenton, Washington fell back to the banks of the river just as night fell.  Cornwallis, being the typically over-cautious British general that he was, postponed his attack until the morning and sent his army to bed.  But while they slept, Washington employed the old leave-the-campfires-burning trick and slipped around the British army and marched on Princeton.  Cornwallis was awakened by the sound of fighting to the north. He quickly roused his army; but by the time they reached Princeton, Washington had driven the British garrison from the town and was on his way Morristown, New Jersey where he established an easily defended winter camp.

American victories at Trenton and Princeton could not have come at a better time.  After the disaster at New York, the Patriots needed their morale boosted and Washington needed his credibility restored. Within less than a week, the American effort gained an entirely different complexion, and the prospects for 1777 looked far more encouraging.