While Marshal Nicolas Soult invaded northern Portugal in early 1809, two other French forces stood ready to cooperate in the subjugation of Portugal. Pierre Belon Lapisse's division lurked near Ciudad Rodrigo while Victor's I Corps operated in the Tagus valley. A weak force under Robert Thomas Wilson watched Lapisse while Alexander Randoll Mackenzie's Anglo-Portuguese corps kept an eye on Victor. After being outgeneraled by Wilson, Lapisse marched south to join Victor. As Sir Arthur Wellesley's Anglo-Portuguese army disposed of Soult's corps, the detachment under Mayne moved to occupy Alcántara.