The Fokker D.XIII; Germany’s Secret Fighter

October 17, 2023

With their defeat in the First World War in 1918, and the subsequent signing of the Treaty of Versailles in 1919, the German military found itself essentially gutted of much of its strength and forbidden from building up its capability in the future. Strict provisions were put in place that prevented Germany from either developing or possessing a range of weapons, most notably submarines, poison gas and aircraft.

But the Reichswehr, as the post-war German military was called, had few illusions about the fact that there was going to be future wars and were not going to let the provisions of Versailles prevent them for preparing for them. Barely had the blood dried into the ground on the battlefields than German companies were busy setting up front corporations in other nations to continue development of the next generation of weapons.

Indeed, though the rapid expansion in size and capability of the German military after 1933 is attributed to Hitler’s taking power and his plans of conquest, the Nazi’s were able to make these plans reality so swiftly because of the extensive and secret work that had been conducted already under the Weimar Republic.

Key amongst these secret military development projects was the preparation for creating an air force. After all, such an organization doesn’t just need modern aircraft, it needs plenty of trained pilots and ground crews.

And here the anti-militarization provisions of Versailles really presented a problem for the Germans. Because while they were allowed to maintain both an army and a navy, though both heavily restricted, in terms of air power the victorious Allied powers had placed a complete ban on Germany not just having military aircraft, but from even being allowed to build them. They also paid close attention to any German efforts that appeared to have the potential for training combat pilots.

Germany was able to continue to create a pool of basically qualified flyers by establishing glider schools, but this was still a far cry from having a worthwhile body of combat pilots.

Things really came to a head in January 1923 when, following repeated defaulted payments by Germany on the war reparations they owed, the French and Belgians occupied the Ruhr Valley, the heart of Germany industry. The inability of the defanged German military to offer any sort of resistance to this inspired the Reichswehr high command to actively plan to break the provisions of Versailles and acquire fighters as quickly as possible to fight against the occupation.

To this end they clandestinely contacted Anthony Fokker, who had been a major builder of aircraft for the Imperial German Air Service during the war. Fokker had returned to his native Netherlands after the German defeat and established a new and thriving aircraft factory outside of Amsterdam and, in violation of international law, was more than happy to sell his old associates fighter aircraft. Indeed, he would sell them a thoroughly new fighter he was developing that was as formidable as anything else flying at the time; the Fokker D.XIII.

The new fighter was built with a metal tube structure skinned in fabric for the fuselage. The wings, which were staggered and of unequal span, were built with wooden struts with plywood skin.

Powerplant was the British Napier Lion IX that produced 570hp, while armament was a fairly typical twin rifle-caliber machine guns mounted above the nose in front of the pilot.

The whole aircraft was extremely streamlined and, as said, one of the most formidable fighters flying. Compare it to the slightly later Gloster Gamecock, for example, which was of all-wooden construction, had the same level of armament but was quite a bit slower, and the Fokker certainly was an excellent aircraft.

Because of the prohibition on Germany having military aircraft a subterfuge was set into play, with a fake order for fifty Fokker D.XIII being placed, on paper at least, by Argentina and Fokker set to work building the new aircraft.

However, things became far less urgent when a deal was struck between the various nations at odds with one another and the crisis abated in September 1923. The German military’s plans for war, the Ruhrkampf, were abandoned and Fokker was left with fifty fighters in advanced production that once completed went into storage while the German’s figured out what to do with them.

Which actually didn’t take all that long.

Despite the Ruhr crisis being resolved it did cause the German military to escalate their secret development projects, and the need for an air force training program was identified as an utmost  priority. The problem was, where could the German’s establish a combat pilot training program where the eyes of not just Allied intelligence could pry, but that of the new, and highly suspicious Polish and Czechoslovak nations as well?

There really was only one answer; the Soviet Union.

In 1924 a commission of German officers and aviation experts was sent to that country to negotiate the setting up of a covert program for training fighter pilots and ground crews, as well as cooperating on tactical and aircraft development. This saw the establishment of a new training facility at Lipetsk, some 270 miles southeast of Moscow.

Initially, the German’s had planned to equip this school with the Junkers J.22 fighter. This was an extremely advanced design that was scheduled to be constructed in the Soviet Union to become the Red Air Forces new fighter.

As part of the overall covert development program, Junkers had established a factory just outside Moscow to develop and build their own aircraft away from prying eyes, and the J.22 was anticipated to be a great fighter, with all-metal construction, monoplane wing and even jettisonable external fuel tanks.

Problem was, it turned out to be rubbish. Flight tests showed it to have extremely poor stability and, despite much reworking, by late 1924 it was plain that the J.22 was not going to be Germany’s new secret fighter. But fortunately, they had a perfectly viable alternative in the shape of the Fokker D.XIIIs that were sitting around in the Netherlands.

In 1925 these were shipped to the Soviet Union and onward delivered to Lipetsk, where they were soon in use providing Germany’s future combat flyers and their support staff with valuable experience.

Fokker had also been busy pushing the aircraft at air salons and demonstrations in 1924/5, where it caused some interest. In July 1925 the Fokker D.XIII set four new airspeed records while carrying payloads of 250-and-500kg, and the aircraft was credited with a top speed clean of 170mph (274km/h).

Despite this the aircraft didn’t achieve any further sales than the fictitious Argentine/covert German one, but those aircraft literally laid the groundwork for the fearsome Luftwaffe of World War Two. The Lipetsk fighter school was operational between 1926 and 1933, turning out one hundred and twenty pilots and one hundred observers, as well as a great number of support personnel, providing the kernel that would ultimately build into a force of tens of thousands.

Naturally, the heavy use for training new pilots took a toll on the Fokker D.XIII’s, and by the time the training mission was abandoned only thirty remained operational.

These were handed over to the Soviet Air Force and entered service with them, at which point the story of the Fokker D.XIII goes cold and they disappeared into obscurity, assumably gradually expended by the Soviets as advanced trainers and eventually going to scrap as that country developed its own more advanced successor aircraft.

But honestly, considering the role that the Luftwaffe would play in the coming turmoil of the Second World War, the part the Fokker D.XIII played is definitely worth noting. After all, there can’t be many occasions where a mere fifty aircraft had such a huge impact on aviation history.



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