Construction began in 1940, in the first months of the German occupation, and the airfield's first purpose was offensive: a launching point for operations against England. Later in the war its role inverted, and Grove became a base for defensive fighters, among them the twin-engined night fighters stationed in Jutland.

The detail that reveals the scale of the undertaking is not the runways but the railway. The site sat close to the Alhedebanen line, and the Germans laid a siding complex alongside it - Grove Sidespor, described as the longest siding facility in Denmark - to move ammunition, fuel, and building materials in by the trainload. An airfield large enough to need its own freight yard was not a temporary arrangement. It was infrastructure, built to stay.

British forces advanced into Denmark in May 1945, and the airfield was handed over to Captain Eric Brown of the Royal Navy, attached to the Royal Aircraft Establishment. Brown was a test pilot of extraordinary range, and what he found parked at Grove was a prize: nine Arado Ar 234B reconnaissance bombers - jet aircraft, and among the most advanced machines the Luftwaffe had put into service. He and his colleagues flew them out to Farnborough, where British engineers took the German jet programme apart bolt by bolt.

Other images from that summer are less triumphant and more strange. In August 1945, German prisoners of war were photographed at the base painting British markings onto a Messerschmitt Bf 110 night fighter - the men who had built the place now repainting its aircraft for its new owners.

By December 1945 the airfield had been taken over by the Danish Civil Air Defence, and its purpose changed completely. Grove became a refugee camp for roughly 22,000 German civilians - people displaced by the collapse of the Eastern Front and the end of the war, stranded in a country that had just spent five years under German occupation and had little appetite for hosting them. Control passed to the Royal Danish Army in January 1946, and the camp continued until 1949.

What those years cost is recorded in the ground. Two cemeteries near the base hold the dead from the camp period: about 1,500 graves at Gedhus and about 1,300 at the refugee cemetery at Grove. Nearly three thousand people who had already lost their homes did not survive the wait to be sent somewhere else. The rows are quiet, well kept, and easy to miss from the road.

In 1947 the Danish Army Air Corps established a flying school, maintenance centre, and logistics office at Karup, preparing for Gloster Meteors, Airspeed Oxfords, and Supermarine Spitfires. When the Royal Danish Air Force was formed in 1950, the site was renamed - officially becoming Flyvestation Karup on 8 February 1951.

What followed was the Cold War in aircraft types. Tactical Air Command moved in during 1955. American machines filled the hardstands through the 1950s and 1960s: Lockheed T-33 Shooting Stars, Republic F-84 Thunderjets, the RF-84F reconnaissance variant, F-100 Super Sabres. In 1970 Denmark bought two squadrons of Swedish Saab 35 Drakens and based them here. Through the 1980s and 1990s, as smaller units were consolidated out of Værløse near Copenhagen and Vandel in southern Jutland, Karup absorbed them, and in 1993 the Army Operational Command arrived too. The heath airfield had become the nerve centre.

The base today covers around 3,000 hectares, of which only about a third lies inside the operational area marked by a 17-kilometre fence. Helicopter Wing Karup is the resident flying unit, alongside the RDAF Flying School, the Air Control Wing, the Specialist School, the Training Centre, the Expeditionary Air Staff, and the Operation Support Wing, plus the operational commands of both the Army and the Air Force. The arms and technology company Danish Aerotech maintains facilities inside the perimeter.

And then, on the same concrete, there is Midtjyllands Airport - EKKA, IATA code KRP - running civilian traffic to Copenhagen and seasonal charters to Palma de Mallorca. Four runways, the longest around 10,000 feet, serve both. Passengers boarding a holiday flight in central Jutland are taxiing across an occupation-era airfield, past helicopters, without any particular reason to notice.