On 11 December 1808, General John Moore led a British army numbering 22,500 foot soldiers, 2,500 horsemen, and 66 artillery pieces northeast from Salamanca. Moore had written to a fellow general, "if the bubble bursts and Madrid falls, we shall have to run for it." Soon after, Moore learned that Napoleon had seized Madrid and that over 200,000 Imperial French troops were in the field. Nevertheless, the British general decided to strike at Marshal Nicolas Soult's isolated II Corps in the north of Spain. When the British cavalry routed Soult's horsemen at Sahagún on 21 December, the French general was completely surprised. Meanwhile, Napoleon found out what was going on and ordered 80,000 troops to march north to annihilate the British.