AA & Anti-Tank. This Cannon did it all 
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88mm FLAK Cannon
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"The name applies to a series of related guns, the first one officially called the 8.8 cm Flak 18, the improved 8.8 cm Flak 36, and later the 8.8 cm Flak 37. Flak is a contraction of German Flugzeugabwehrkanone[3][N 2] meaning “aircraft-defense cannon”, the original purpose of the eighty-eight. In English, “flak” became a generic term for ground anti-aircraft fire. In informal German use, the guns were universally known as the Acht-acht (“eight-eight”)."
-From the Article