Modrow was born in 1908 in Stettin, then a Prussian port, today the Polish city of Szczecin. He learned to fly as a civilian in 1929. Through the early 1930s he worked for SCADTA, the Colombian-German Air Transport Society, then flew the long postal routes between Germany and South America for Deutsche Luft Hansa. When Germany invaded Poland in September 1939, Modrow was 31 years old with a logbook full of ocean crossings - exactly the kind of pilot the Luftwaffe wanted for its long-range maritime aircraft. He was posted to a special-purpose group flying the enormous, slow Dornier Do 26 flying boat, ferrying supplies into Narvik during the Norwegian campaign. On 28 May 1940, at anchor in the Rombaksfjord, his Do 26 and a sister aircraft were attacked by Hawker Hurricanes of No. 46 Squadron led by a New Zealand flight lieutenant, Patrick Jameson. Both flying boats were destroyed. Modrow was severely injured. He would spend most of a year in convalescence.

By the time he returned to the front lines in late 1943, the air war had changed shape. RAF Bomber Command had abandoned daylight raids years earlier; the bombers came at night now, in streams of hundreds, threading north and east across occupied Europe toward German cities. To meet them, Generalmajor Josef Kammhuber had built a defensive belt that stretched from Denmark to the French coast - a chain of overlapping control sectors, each equipped with ground radars, searchlights, and an orbiting night fighter. Each sector was called a Himmelbett, literally a canopy bed. From the ground, controllers vectored their fighter into the bomber stream until the pilot's own onboard radar - the Lichtenstein set, mounted on antennas that bristled from the nose like fish bones - could acquire its target. The bomber crews flying through the Himmelbett did not see the men hunting them. They felt the cold of the unpressurised fuselage, watched their breath ice on the windows, and listened for the sudden hammering of cannon shells that meant another aircraft in their formation had ceased to exist.

Modrow's hunting ground was the airspace over the Netherlands, particularly the corridor stretching from Venlo in the south to Zoutkamp on the Groningen coast. The He 219 he flew was an unusually capable aircraft - faster than the Messerschmitt Bf 110 it gradually replaced, easier to land in bad weather, and equipped with cannon heavy enough to dismantle a four-engined bomber in a single pass. Modrow became the type's leading combat advocate at exactly the moment the German Air Ministry was debating whether to cancel its production. His success rate kept the Heinkel alive. In a single night, 21-22 June 1944, RAF Bomber Command sent more than seven hundred Lancasters and Halifaxes against the synthetic oil refinery at Wesseling, south of Cologne. No. 44, No. 49 and No. 619 Squadrons each lost six aircraft. Four of those Lancasters were claimed by Modrow alone, between 01:12 and 02:01 in the morning. Each Lancaster carried seven men. Most of them were under twenty-five.

It is easy, in summaries like this one, to lose the bomber crews inside the arithmetic. The numbers in Modrow's logbook were real young men. The first Halifax he shot down, on 31 March 1944, was HX322 of No. 158 Squadron, piloted by Flight Sergeant Albert Brice. Six of its seven crew died near Caumont in northern France. Only the wireless operator, Sergeant Kenneth Dobbs, parachuted clear. The same night - the Nuremberg raid - the RAF lost 106 aircraft and as many as 545 men: the worst single night in the history of strategic bombing. Two months later it was Joe Downey, the Mosquito pilot over the IJsselmeer, who lost his aircraft and his life while his navigator parachuted into Dutch farmland. Other names recur in the Canadian squadron records, in the prisoner-of-war lists, in the cemeteries scattered across Belgium, France and the Netherlands. By the time he claimed his last victim, a Halifax bomber on 5/6 January 1945, Modrow had killed somewhere on the order of two hundred Allied airmen in 109 night sorties.

Modrow survived the war. He had received the Knight's Cross of the Iron Cross on 19 August 1944, presented at Venlo by Generalmajor Walter Grabmann a few weeks later, and the German Cross in Gold on New Year's Day 1945. When West Germany rebuilt its armed forces, he served in the Bundeswehr until 1964 and retired as a lieutenant colonel. He died in Kiel in 1990 at the age of 82. The Heinkel He 219 he advocated for was largely abandoned after the war - only a handful of airframes survived, one of them now in the Smithsonian's restoration hangar at Dulles. The Kammhuber Line, the elaborate apparatus of radar and searchlight and waiting fighter, ended at Germany's defeat. What remains, mostly, is a quieter inheritance: the names on RAF Bomber Command's roll of honour, the Commonwealth war graves in Dutch towns, the wreckage occasionally pulled from the IJsselmeer when divers find another Lancaster on the bottom. The airspace where Modrow worked is empty now. The villages below his patrol routes - Alkmaar, Deelen, Zoutkamp - never quite forgot what fell out of their sky.