Over the next three years it sent its best pilots and newest aircraft — the Bf 109, He 111 and Ju 87 Stuka — to join the fight and develop the Luftwaffe’s doctrine, tactics and combat experience.

The Spanish Civil War proved to be a superb training ground for the Blitzkrieg that would soon be unleashed across Europe.

As told by Dr James S. Corum in his book Legion Condor 1936-39 the Luftwaffe develops Blitzkrieg in the Spanish Civil War, the Luftwaffe also learned many tactical lessons in Spain, but the most important one was a revolutionary change in fighter combat that would eventually change the way all air forces fought. One of the most important single figures of the Spanish Civil War was not a high-ranking officer, but rather a fighter pilot who arrived as a first lieutenant and replacement fighter-squadron commander. Yet this young officer, in a very short period, would play a central role in revolutionizing fighter tactics. Werner Mölders was horn in 1913 in Westphalia. His father, a reserve officer, was killed in the battles of 1915, and he was raised by his mother’s family in central Germany. He graduated from one of the top high schools of Germany in 1931, and with his Abitur (university entrance certificate) he applied to join the army as an officer aspirant. He was appointed to the 2nd Prussian Infantry Regiment and he went through the very thorough and intensive three year officer education programme. In March 1934, Mölders was commissioned as a lieutenant and assigned to the new Luftwaffe. Mölders entered flight training and graduated at the top of his class. He then proceeded to the special six-month fighter-pilot course, and again graduated at the top in June 1935. In 1936, he was promoted to first lieutenant. Mölders took over command of a training squadron and served under group commander, Major Theo Osterkamp, who would also become one of the key figures in the Luftwaffe fighter force. In March 1937, Mölders was given command of Jagdgeschwader 334, and proved himself to be an exceptional commander as well as instructor.

Mölders volunteered to go to Spain, arriving in March 1938. He was assigned to take over Adolf Galland‘s fighter squadron, which was still equipped with the He 51 but in the process of transitioning to the Bf 109. In May 1938, after a short transition period,  took over as squadron commander. Mölders was soon involved in the very tough fighting around Aragon and over the Ebro. He scored his first victory over an I-15 on Jul. 15, 1938. Between July and Nov. 3, 1938, Mölders would rack up 14 confirmed aerial victories, which made him the top German ace of the Spanish Civil War. His victories included two I-15s, 12 I-16s, and one SB-2 bomber. As Mölders led his squadron into the Aragon and Ebro battles, he began work on developing a revolutionary new tactical system for the fighters. The system used by all the major air forces up to that time had scarcely changed from World War I, in which squadrons of 9-12 aircraft would fly a very tight formation, usually based on the ‘V’ or Flight of three aircraft. The tight aircraft formations, inherited from World War I combat, came from a period in which fighter aircraft did not have radios and needed to use hand signals; to observe these signals, pilots had to be sufficiently close to their flight and squadron leaders. Now that aircraft were more than twice as fast as the World War I biplanes, and equipped with radios, a Great War tactical system made no sense. Mölders developed a system based on pairs, in which one pair of wingmen, called a Rotte, would look out for each other, one usually forward and the other slightly above and behind. The Rotte could be enlarged with another Rotte, to make a loose formation of four aircraft called a Schwarm. This four-aircraft Schwarm replaced the three-aircraft flight, and was also called the ‘finger-four formation’ because it looked like the fingers of a hand, with two fingers, the second slightly ahead, and then a pair of fingers, the second aircraft again slightly leading.

Now fighter squadron tactics would he based on pairs and small groups. Instead of a 30m spread between aircraft, as in the old tactics, aircraft could now fly 300-500m apart, since radio contact provided them with effective communications. By spreading out and pairing the fighters, a more extensive area of the sky could be patrolled and observed, and the danger of midair collisions was largely eliminated. Given the speed of the Bf 109, any Schwarm engaging in combat could be quickly joined by other Schwarms. Mölders trained his fighter pilots in the new tactics. He also developed a new way to turn a flight in combat. Previously, a tight change of direction for a flight or squadron was an exceptionally dangerous manoeuvre because of the very narrow separation between aircraft. Now, with a wider separation, Mölders invented the crossover turn, in which aircraft would simply pivot 90 degrees and switch positions.

The new fighter tactics proved so successful against the Republican pilots that when Mölders completed his tour, he was brought back to the Luftwaffe staff and given a special mission in the Fighter Inspectorate: to develop and train the Fighter Command in this new tactical system. Mölders only served eight months in Spain, from March to December 1938, when he turned over his squadron to Hubertus von Bonin and received his promotion to captain. However, those eight months in Spain assured Mölders reputation as a superb leader and fighter tactician. Mölders was quickly promoted up to command groups and wings. He was a major and group commander in the 1940 campaign in France and by 1941 had achieved the rank of colonel, or Oberst, and commanded a fighter wing in Russia. That year he was appointed Inspector of the Luftwaffe Fighters, but served only a brief time in that position as he was killed in an accident in November 1941. He was the first fighter pilot in the world to gain more than 100 confirmed aerial Victories. The impact of his new tactics was so dramatic that eventually, all the combatant air forces of World War II would adopt the system of pairs, the finger-four formation, and the crossover turn that had been invented by Mölders.