Sir John Moore led a British army into the heart of northwestern Spain with the aim of aiding the Spanish in their struggle against French occupation. However, Napoleon had entered Spain at the head of a large army intending to reestablish French interests. This, together with the fall of the Spanish capital Madrid to the French, made the position of the British army untenable. Moore, whose headquarters was at Mayorga, was aware that he must retreat towards the coast in the face of the overwhelming odds ranged against him. However, he was also aware that Marshal Soult's apparently unsupported corps was nearby, on the Carrión River, and before beginning his retreat he wished to make a strike against Soult. As part of this design the cavalry under Henry, Lord Paget were sent towards Soult, as a reconnaissance in force, ahead of the infantry.