German Flak 18 cannon..
   The 37 mm Flak 18 was an anti-aircraft and and also anti-tank cannon, that saw widespread service in the Second World War. The cannon was fully automatic and effective against aircraft flying at altitudes up to 4,200 m. The cannon was produced in both towed and self-propelled versions. 
Flak is a contraction of German Flugzeugabwehrkanone, meaning "aircraft-defense cannon". 

Flak 18 with score stripes

German soldiers putting a camouflage net over an 88 mm Flak-18 anti-aircraft gun emplacement. 

88 mm anti-aircraft battery

German troops setting up their 88-mm Flak gun into firing position on a snow covered field; Russia, 22 December 1943.
