Following the British retreat and the evacuation of Sir John Moore's army after the Battle of Corunna in January 1809 it was found that a sizeable number of men remained detached from the regiments within the British Army in Portugal. This included those convalescing in hospital in Lisbon, those who became separated during the retreat and other miscellaneous stragglers. As these men's regimental headquarters had been returned to England they were left without organization or logistical support. Brigadier-General Alan Cameron, commanding the British force at Oporto, gathered these men together under the auspices of a temporary battalion of detachments. This was primarily a means of bringing the men into the organizational structure of the army so that they could be supplied with rations and clothing to reduce the likelihood of them resorting to "every possible excess that could render the name of a British soldier odious to the nation". Later the unit would see active service in battle in a manner similar to more conventional battalions.