Neither did Udet have much to fear from Göring. As elected chairman of the Richthofen Veterans Association, Udet had expelled Göring, the unit's last commander. Udet accused Göring of falsifying his First World War record and victory claims and said he could prove it. Milch said that Göring admitted it was true, and was frightened of Udet.

By now Milch had few friends. Heartily disliked by Göring, he found little support from the Luftwaffe General Staff. In spite of this, the irrepressible Milch, working like a beaver, consolidated his authority, and in certain areas increased it. When the Spanish Civil War started and Franco asked for Hitler's aid, Milch instantly recognized it as a chance to increase his power. He took charge of the intervention.

By early 1937 Milch had a small experimental air force unit operating in Spain. One of its first missions had been the air-transporting of 10,000 fully equipped Moorish infantry from Tetuan, in Spanish Morocco, to Seville. They used Junkers Ju 52/3m aircraft, and the movement went almost without a hitch. In some respects it was as significant as any of the Condor Legion's combat actions.

The Condor Legion's commander was Sperrle, who later became an Air Fleet commander in the Battle of Britain. His Chief of Staff was Wolfram von Richthofen, a dive-bombing and close-support specialist. (He was a cousin of the First World War ace.) The Luftwaffe's first taste of combat was a terrible disappointment for Göring, Milch, and the High Command. The Junkers Ju 52/3m proved unsuitable for bombing, and most bombing turned out to be far less accurate than had been hoped. The Heinkel He 51 biplane fighters were inferior to the I-16 fighters (supplied to the other side by the USSR) in speed, climb, manoeuvrability, and armament. Reluctant to believe this, the German flyers often misidentified them as "Gurtiss fighters." But as German skill improved and newer German aircraft arrived, things got better: Berlin's apprehension turned into equally wrong complacency. When Dornier Do 17 and Heinkel He 111 bombers proved faster than enemy fighters the Schnellbomber concept seemed vindicated. Rashly the men in Berlin concluded that bombers would never require fighter escort.

The Junkers Ju 87 dive bomber also exceeded expectations, and its small bomb-load was more than compensated for by the fast turn-around time at its bases: some of the units completed half-a-dozen missions per day. And von Richthofen's close-support techniques proved decisive in some actions, even though the war's front line was notoriously difficult to see. There was a shortage of aircraft radio but the airmen relied on signals spread out on the ground. They did little to improve air-to-air or air-to-ground radio. This, too, was to prove a grave error.

The Messerschmitt Bf 109s arrived to take over the fighter combat tasks. Heinkel He 51 biplanes were already adapted to carrying 10-kg high-explosive bombs and improvised petrol bombs. This flat-trajectory bombing in support of infantry attacks became a specialized technique of German (and Allied) light-bomber squadrons. It was one of the few new methods to evolve in the Spanish fighting.

The Luftwaffe's first building programme had begun in January 1934; it went to war in September 1939. By 1937 there was clearly little time left for redesigning the Luftwaffe's aircraft. These aircraft types that fought in Spain — Bf 109s, He 111s, Ju 87s, Ju 52s — remained the basis of the Luftwaffe's strength right up until the end of the Second World War.

Milch sent Hugo Sperrle's Condor Legion to Spain to assess the aircraft already in production. With this in mind, many different aircraft types were sent there, including even float-planes. The flying personnel were rotated after six months to provide combat experience for as many crews as possible. All ranks were encouraged to send reports to a specially constituted department of the Air Ministry.

Just as men from von Seeckt's Defence Ministry provided the Luftwaffe with its staff and its Air Fleet commanders, and Lipetsk (the secret training school in Russia) provided its field commanders, so now did Spain provide combat specialists. Men such as Adolf Galland and Werner Molders came back from leading a fighter Staffel in Spain to revolutionize the formations and tactics of the fighter arm.

…was an outstanding personality of this period. Born in 1912, of Huguenot ancestry, Galland, like so many other Luftwaffe aces, was attracted to the sport of gliding while still a teenager. Accepted by the Air Transport School at Brunswick, Galland was soon selected for the secret Luftwaffe. At 22 years old he was an instructor at the famous Schleissheim Fighter Pilot School. Galland went to fight in Spain but, flying a Heinkel HE 51 biplane, deliberately avoided combat with the far superior Russian- and American-made enemy monoplanes.

The poor performance of the He 51s caused them to be relegated to the infantry support role. Galland pioneered these experiments and produced a considerable body of written material about the use of aircraft in support of ground forces. This fitted very well with the dive-bombing theories of Udet, which were by now enthusiastically received by senior officers, including General von Richthofen, Chief of Staff of the Condor Legion, who would soon command the Junkers Ju 87 Stuka units in the Battle of Britain.

And so Galland found himself trapped into the role of ground-support air specialist. As the Bf 109s were shipped to Spain, Galland handed his command over to a young man who was to become his rival as the most famous fighter pilot in Germany "Vati" ("Daddy') Molders. Molders began to use the monoplane fighters to win victories, Galland returned to Berlin and a job in the Air Ministry.

In September 1937, as the Condor Legion fighter unit near Santander, Spain, flew seven sorties a day against crumbling resistance, senior Luftwaffe officers paid an official visit to Britain. Milch and Udet were invited to inspect RAF Fighter Command at Hornchurch, a key airfield in the defences of London. The aircraft there were Gloster Gladiator biplanes which, like the Hawker Fury fighters also in service, were slower than the Luftwaffe bombers.

There were virtually no monoplanes of any sort in RAF service at this time. The Hurricanes and Spitfires were suffering new delays caused by a modification to the nose that an engine improvement demanded. It is sometimes said that this was part of a nicely timed deception plan, for the RAF's first Hurricanes reached 111 Squadron during the following month. Why such a provocative deception would have been desirable is not explained.

Although by tradition subordinate to the army as a fighting force, the German navy was independent of it in a way that the Luftwaffe was not. In the spring of 1940 the German navy fought a brilliant and daring campaign in Norwegian waters. This had to some extent been made possible by the navy's B-Dienst cryptanalytic department which, by the time war began, was able to read even the most secret of the British Admiralty's messages, having broken the codes and ciphers.

In the spring of 1940 the German navy's prestige was high. Its strategists demanded more steel for submarines and were preparing a surface fleet that, with Italian help, might control the Mediterranean by 1942.

But the navy needed time to recover from the grave, but worthwhile, losses that the conquest of Norway had caused it. So the Admirals had little enthusiasm for hasty and dangerous invasion plans that would hazard their few remaining ships in the Straits of Dover.