Messerschmitt Bf.109D - German users, part one.

The Bf.109D was developed from the V10 and V13 prototypes and was powered by a Junkers Jumo 210D engine. D-0 and D-1 sub-variants were armed with two nose-mounted 7.92mm (0.312in) MG17 machine guns plus another two wing mounted ones. D-2 was a prototype with an engine-mounted machine gun but, as previous experiments, it failed and the idea was discarded. The D-3 sub-variant was a version similar to the Bf.109C-3 with 20mm MGFFs (0.787in) in the wings instead of MG17s.
Six hundred and forty seven of Bf.109D were manufactured. Most of them licensed ones mande by Focke-Wulf, Erla Maschinenwerk, Fieseler, Arado and AGO. Messerschmitt themselves only manufactured 4 of them, probably the D-0 sub-variant which was the pre-production version.
When appeared, the Bf.109D became the standard Luftwaffe fighter during the years before the start of the World War II. However, they saw only limited service during the war as most of the 235 Bf.109D that were still in service during the Polish Campaign, were taken out of active service and replaced by the Bf.109E. Some of them served as night fighters until early 1940 when they were definitely withdrawn from service.

Sources:
1. https://en.wikipedia.org/wiki/Messerschmitt_Bf_109_variants#Bf_109_A/B/C/D
2. Salamander Books - The Complete Book of Fighters
3. Signal Squadron - Aircraft In action 44 - Messerschmitt Bf-109 in Action Pt.1