Following reports that Franco and the Germans were planning an invasion of Gibraltar, Churchill was allegedly convinced, in the summer of 1940, that Spain was about to enter the war on the side of Hitler. Hillgarth argued, however, that Franco’s high command was corrupt and that the generals were not paid much and would consequently be open to bribery.
The Spanish banker, Juan March, was chosen for the job and made responsible for the organisation of payments to the generals. March had dealt in contraband tobacco during the First World War and made a fortune. He had also sided with Franco during the Spanish Civil War. It thus remains unclear as to whether or not he was a double agent. He may have stayed in pay with the Germans whilst working for the British.
The 10 million dollars bribe money was deposited in a bank in New York, but the US Treasury froze the account in the belief that the money was being used to help Hitler and the plan nearly collapsed. When the money was eventually released, however, the Spanish generals received between 3 and 5 million dollars in 1942 alone. In 1943 Spain declared complete neutrality; nevertheless, Franco did allow Hitler to use Spanish naval bases during the war and Italian planes refueled at Spanish airbases. Spain also helped the Germans to build observations posts around Gibraltar for German spies.