Wellington's use of intelligence developed throughout his military career. Arguably, his experiences in India taught him the importance of intelligence, but it was during the Peninsular War that he honed his analytical techniques. As the war progressed, he developed sophisticated methods for the integration of strategic intelligence - largely gathered by civilian agents - with operational intelligence - collected by military personnel. This allowed him to develop operational conceptualisation, which in turn contributed to the successes he achieved over the French forces in Iberia. However, more than anything, it was his considered use of intelligence, combined with intricate deception operations in the latter stages of the conflict, which deprived the French of reliable intelligence on his own movements, and demonstrated his understanding of the importance of intelligence. This article investigates Wellington's increasing awareness of the importance of intelligence and deception during the Peninsular War.