The British called them Hessians, which is only half right. Here is who they actually were and what they wore.
Quick answer. The Hessian soldiers who fought for Britain in the American Revolution were German troops hired from Hesse Kassel (about half the total), Hesse Hanau, Brunswick, Ansbach Bayreuth, Waldeck and Anhalt Zerbst. Infantry wore dark blue wool coats with regimental facings in yellow, red, white or crimson. Grenadiers wore brass fronted mitre caps; musketeers wore tricornes; jaegers wore green coats and round hats. The best were among the best disciplined infantry in Europe.
Who the Hessians were
German states in the 18th century maintained large professional armies and leased them to larger powers in exchange for subsidies. Britain, with limited native manpower, hired German troops in every war of the century. In the American Revolution, Britain contracted around 30,000 soldiers from six German principalities. The largest contingent came from Hesse Kassel (about 17,000), which is why all German auxiliaries became known as Hessians in English usage, even those from Brunswick or Ansbach Bayreuth.
The Hessians were not mercenaries in the modern sense. They were state soldiers whose services had been contracted to Britain by their rulers. The individual soldier was conscripted and could not refuse the deployment.
The musketeer uniform
A Hessian musketeer in 1776 wore a dark blue wool coat with regimental facings on the collar, cuffs, lapels and turnbacks. Each regiment had distinct facings: red for the Regiment von Donop, yellow for the Regiment Erbprinz, white for the Regiment von Mirbach, crimson for the Regiment von Trumbach. Yellow waistcoat, yellow breeches, long black gaiters, tricorne with lace trim. Buttons were brass or pewter with the regimental number. The look resembled a Prussian uniform rather than a British one, which is correct: the Hessian army was closely modelled on Frederick the Great's Prussia.
The grenadier mitre cap
The most distinctive Hessian item was the grenadier's mitre cap. A tall brass fronted conical cap with heraldic devices in brass, often the regiment's coat of arms or a crowned cipher. The mitre cap was Prussian in origin, adopted from the Prussian grenadier guard regiments. Hessian grenadiers wore it throughout the American campaign, which contributed to their fearsome visual effect. Fusilier regiments wore a slightly different mitre with brass fronted peak, which was easily mistaken for the grenadier version at a distance.
The jaegers
The Hessian jaeger battalions were light infantry armed with rifled muskets. Dress: green wool coat with crimson facings, green waistcoat, grey trousers, short gaiters, round hat with green plume. The jaeger was recruited from foresters and gamekeepers in Germany and was expert at skirmishing in close country. In America they were particularly feared by Continental riflemen because they could out shoot and out woodcraft most American riflemen. The jaeger pattern influenced British light infantry development.
Brunswick and other contingents
Brunswick troops wore dark blue coats with yellow facings for the regular infantry and sky blue coats with yellow facings for the dragoons. The Brunswick dragoons, dismounted in America, served as infantry. Ansbach Bayreuth troops wore dark blue with red or white facings. Waldeck wore dark blue with yellow. Each contingent kept its own regimental identity, which made the German auxiliary force one of the most visually varied armies of the war.
After the war
Of the roughly 30,000 Hessians who served in America, about 7,500 died (mostly of disease), 5,000 settled in America after the war, and the rest returned to Germany. The Hessian settlement in Pennsylvania became a significant element of the state's German American community. Hessian regimental records are well preserved in Marburg, Germany, which is why we know so much about individual soldiers.
Common questions
Were all Hessians from Hesse?
No. The term Hessian covered German auxiliaries from six principalities: Hesse Kassel, Hesse Hanau, Brunswick, Ansbach Bayreuth, Waldeck and Anhalt Zerbst.
What colour was a Hessian uniform?
Dark blue for most infantry, with regimental facings in yellow, red, white or crimson. Jaegers wore green coats.
Did Hessians wear mitre caps?
Grenadier companies and some fusilier regiments did. Line musketeers wore the tricorne.
How many Hessians died in America?
About 7,500 of 30,000 died, most from disease rather than combat. Around 5,000 settled in America after the war.
Can I buy a replica Hessian uniform?
Yes. Reenactor tailors in Germany and the US build Hessian pattern coats, mitre caps and jaeger dress for the many active Hessian reenactor units in both countries.