Though some maintain that he was not at his best as a leader in battle, as a strategist Espoz y Mina was very successful and displayed great organizing capacity. The French authorities were compelled to allow him to levy customs dues on all goods imported into Spain, except contraband of war, which he would not allow to pass without fighting. The money thus obtained was used to pay his bands a regular salary. He was able to avoid levying excessive contributions on the country and to maintain discipline among his men, whom he had brought to a respectable state of efficiency in 1812. Espoz y Mina claimed that he immobilized 26,000 French troops which would but for him have served with Marshal Marmont in the Salamanca campaign. In the campaign of 1813 and 1814 he served with distinction under the Duke of Wellington.