The first deliveries of Do 217s to operational units of the Luftwaffe was the pre-production Do 217A-0 reconnaissance aircraft, which entered service with the Aufklärungsgruppe der Oberfehlshaber der Luftwaffe to carry out clandestine reconnaissance missions over the Soviet Union. Deliveries of the Do 217E started late in 1940, with some aircraft joining another reconnaissance unit, 2 Staffel of Fernaufklärungsgruppe 11, which was also involved in spyflights over the Soviet Union from bases in Romania.

Western Europe

The first bomber unit to receive the Dornier Do 217 was II Gruppe of Kampfgeschwader 40 (II/KG 40) in March 1941, followed by KG 2 later that year. At first these units, based in the Netherlands, were used to carry out minelaying and anti-shipping operations over the North Sea. On the night of 24/25 April 1942, however, Dornier Do 217s of KG 2 took part in an attack on the city of Exeter, the first raid of what was to become known as the Baedeker Blitz. KG 2's Dorniers were heavily deployed during the Baedeker raids, against British provincial cities which were less heavily defended than London, which continued until July that year.

The Do 217 squadrons had little time to recover as on 19 August 1942 the Allies launched an amphibious raid on Dieppe in Northern France, with KG 2 launching almost its entire strength of 80 aircraft in response, losing 20 over Dieppe. It had suffered serious losses of trained personnel during operations during 1942, with the number of combat ready crews in KG 2 falling from 88 at the start of the year to 23 by September.

The Dornier Do 217-equipped bomber units spent most of the rest of 1942 recovering from these losses and re-equipping with the more capable Do 217K and M. Night attacks against Britain re-commencing in January 1943, and continuing sporadically throughout the year, often suffering heavy losses. As an example the Do 217 equipped KG 2 lost 26 complete crews during March 1943. The pace of bombing attacks against Britain increased again in January 1944 with the launch of Operation Steinbock, with the Do 217 equipped I and III KG/2 and I/KG 66 being involved, these attacks continuing until May, with the bomber units again taking heavy losses.

Two Gruppen of the anti-shipping Kampfgeschwader 100 (KG 100) equipped with Do 217s in 1943, with II/KG 100 receiving the Do 217E-5, equipped to carry the Hs 293 guided missile and III/KG 100 the Do 217K-2, with the Fritz-X guided bomb. II/KG 100 made its combat debut against Royal Navy warships in the Bay of Biscay on 25 August 1943, when it near missed the sloop HMS Landguard, while on 27 August, a second attack by 18 Do 217s sank the sloop HMS Egret and badly damaged the destroyer HCMS Athabaskan. This attack lead to a temporary withdrawal of Royal Navy surface ships from the Bay of Biscay until the guided weapon equipped aircraft were transferred to the Mediterranean following the allied landings at Salerno.

The final actions of Do 217 equipped units over Western Europe was against the allied Invasion of Normandy in June 1944, when the remaining Do 217 equipped bomber units, II/KG 2 and III/KG 100 were thrown into action against the Allied landings. Losses were heavy, with III/KG 100 losing 8 of 13 servicible Do 217s in 10 days of operations. As American forces broke out of the bridgehead at the end of July, III/KG 100 sent its remaining Do 217s to carry out attacks on bridges over the Rivers Sée and Sélune with Hs 293 missiles. They managed a single hit on one of the bridges, which remained in use, while seven Dorniers were lost.

Mediterranean and Italy

Twelve Do 217 J-1 and J-2 variants were acquired by Italian Regia Aeronautica between September 1942 and June 1943 for night fighter operations. One Italian unit was equipped: 235a Squadriglia of 60° Gruppo (41° Stormo). Based at Treviso San Giuseppe, then at Lonate Pozzolo, the unit performed poorly. The unit shot down only one enemy aircraft, and lost one of their own, after nearly a year of activity.

When the Italian Armistice with the Allies was announced on 9 September 1943, the Italian Fleet was instructed to sail to Malta to surrender. III/KG 100, based at Marseilles launched an attack from its base at comprising 11 Do 217s armed with Fritz-X guided bombs against Italian warships near Corsica, sinking the battleship Roma and damaging the battleship Italia. The Dorniers were then deployed against the Allied landings at Salerno, damaging the cruisers USS Savannah and HMS Uganda and the battleship HMS Warspite with Fritz X bombs.

The Dorniers of KG 100 continued to be deployed against convoys in the Mediterranean, but by the time of the Anzio landings in January 1944, heavy allied fighter cover and jamming reduced the effectiveness of the attacks, although Hs 293 missiles sank the cruiser HMS Spartan and several destroyers and merchant ships.

Defence of the Reich

Deliveries of the Dornier Do 217J-1 started in March 1942, with night-fighter pilots being unimpressed, considering the type to have poor manoeuvrability and speed. The J-1 was relegated to the training role by summer that year, replaced by the radar equipped J-2 in front-line units. Despite the aircraft's faults, the Do 217 was widely used, being used by 11 night-fighter Gruppen, although it did not completely equip any unit, usually being operated in conjunction with the more popular Messerschmitt Bf 110. The Luftwaffe deployed the Do 217 night-fighter over Italy and the Eastern front as well as in direct defence of Germany, but the type had been phased out of service by mid-1944.

Sources:
Gunston, Bill - The Encyclodepia of the Worlds Combat aircraft, 1976, Chartwell Books, Inc., New York
Brown, Eric, Captain - Wings of the Luftwaffe, 1979, Airlife Publishing Ltd., Shrewsbury
Gunston, Bill & Wood, Tony - Hitler's Luftwaffe, 1977, Salamander Books Ltd., London
Donald, David - The Complete Encyclopedia Of World Aircraft, 1997, Brown Packaging Books Ltd., London
Wikipedia - Dornier Do 217