Frederick II, Landgrave of Hesse-Kassel, had a profitable sideline of hiring out troops.  He did so certainly on behalf of his nephew, King George III of Great Britain during the American Revolution.  He sent a large enough number of troops that the Germanic troops fighting for the British became known as Hessians to the fledgling Americans.

One group of these troops, 3 regiments consisting of 1400 men, was stationed at Trenton, New Jersey, under Colonel Johann Rall.  General George Washington, with the 2400 troops under his command, had the idea for a sneak attack.


George Washington Crosses the Delaware, by Emanuel Leutze:




Washington crossed the Delaware River at night on 25-26 December, 1776, and was on the march to Trenton by 4 AM on the 26th.


The attack plan map:




By 8AM, the Americans had reached Trenton and commenced the attack on Rall and his troops.


The Battle of Trenton map:




Washington and his troops handily won the battle, killing 22 Hessians, wounding 83, and capturing about 1000 of them.  This was a much-needed morale boost after having been beaten in battles in New York.  They evacuated Trenton and retreated back into Pennsylvania with their prisoners.

Capture of the Hessians at Trenton, by John Trumbull:

 

Only 22 dead Hessians and over 1000 captured? I always had the impression that Washington's army slaughtered the Hessians. Hmm. Learn something every day.

Trenton buoyed sagging American spirits and instilled confidence in Washington.  

If you ever study the painting, the third man back from the bow is black.  The men are armed with rifles too, and not muskets.

A bit of trivia, I went to PLDC in the same castle the Hessians were housed and trained at, some 200 years later of course.