The Brunswick-Oels Jägers landed in Lisbon on October 1810. The Regiment comprised 12 companies and a regimental headquarters. Three companies were sharpshooters companies, armed with the Baker rifle. These companies were detached to serve with the British 4th and 5th division, one company served with the 3rd battalion of the 1st Regiment of foot (Royal Scots)., the others were with the Crauford´s Light division.
They served in the peninsula many battles and actions as crack skirmishers, like the famous 95th Rifles and the KGL Sharpshooters.
The uniform was slightly different from the other companies of the Brunswick-Oels.
Distinctively attired in black broadcloth with a silvered death's head badge on their hats, the volunteers were nicknamed the Black Horde or the Black Legion; their more commonly-known title was the result of the Duke's temporary capture of the German city of Braunschweig (Brunswick) from the French in 1809. The Black Brunswickers earned themselves a fearsome reputation over the following decade, taking part in several significant battles including the pre-Waterloo engagement at Quatre Bras on 16 June 1815, where the Duke lost his life. However, recruiting, the replacement of casualties, and finance had always been problematic, and the corps was disbanded in the early 1820s.
The exploits of the Brunswickers caught the British Victorian public imagination: an example of this can be found in John Everett Millais's painting The Black Brunswicker. Completed in 1860, the painting depicts a Brunswicker in his black uniform bidding goodbye to an unnamed woman.