Loison commanded a division in Jean Andoche Junot's Invasion of Portugal in 1807. After first Spain and then Portugal rose in revolt, the position of Junot's 26,000 French troops became difficult. Ordered by Napoleon to send troops to Almeida, Portugal and open communications with Marshal Jean-Baptiste Bessieres, Junot sent Loison with a brigade on this mission. Loison occupied Almeida and marched against Ciudad Rodrigo, chasing off the small Spanish garrison of Fort Conception. But on 12 June 1808 he found Ciudad Rodrigo held by a powerful force and the Spanish countryside in revolt against the French. He quickly fell back on Almeida, reaching there on the 15th. Hearing that the revolt had spread to northern Portugal, he set out for Oporto with 2,000 men. On his way there he was severely harassed by Portuguese guerillas and had to turn back.