At the start of the Spanish Civil War the nationalists sought help for their cause from Germany, following which volunteers from the German Air Force and Army formed what was called the Condor Legion. This force made a significant contribution to General Franco's eventual victory and this included two experimental air units, known as VJ/88 and VB/88. The former's mission was to combat test the new monoplane fighters; the Messerschmitt Bf 109 and the Heinkel He 112. The latter group's task was to test the new twin-engine, retractable undercarriage bombers; the Heinkel He 111, the fast Dornier Do 17 and the Junkers Ju 86. The Heinkels made their combat debut on 9 March 1937, when they attacked Republican held airfields in support of the Battle of Guadalajara. The Heinkel proved superior to the two other German medium bombers, being both faster and carrying a heavier bomb load. Likewise, the Messerschmitt Bf 109 was quickly found to be the better of the two fighters. This book aims to examine the history of the men and machines that served in those units. AUTHOR: Rafael A. Permuy Lopez was born in Ferrol in 1949 and is a reserve Artillery Major. He has a masters degree in Social Communication and a graduate degree in Labour Relations. He has worked as a journalist and column writer for various media in Galicia and for a number of military journals. Lucas Molina Franco was born in Ferrol in 1965. He has a graduate degree in Economics and Business Science and a doctorate in Contemporary History. He has worked as a technical officer in the Regional Government of Castile and Leon while teaching as a university lecturer in Macroeconomics and Business Economics. He is currently editor of ARES, a journal of military history and current military affairs.