Most of the Brunswick troops fought at the Battles of Saratoga, where they were forced to surrender as part of British General John Burgoyne's army.
The Brunswick army had previously served alongside the British during the Seven Years' War (1756-63), successfully campaigning in the Low Countries, but had not been used since.
Colonel William Faucitt, the British emissary, entered into negotiations with Brunswick, and the outcome was the first auxiliary troop treaty of the war between Great Britain and a German state.
It stipulated that Brunswick would make a corps of 3,964 foot and 336 light horse available to Great Britain for service in Europe or America.
The corps, except Regiment Prinz Friedrich (remained at Fort Ticonderoga) and Battalion von Barner, surrendered at Saratoga and became prisoners of war in the Convention Army.