Soon after the fighting at Arras, a story circulated that Rommel had saved the day by using 8.8 cm anti-aircraft guns in the antitank role for the first time ever. How this story gained currency is hard to imagine, for obviously the guns would have been virtually useless against armour unless they had already been supplied with Panzergranate (armour-piercing shells).

[...]

As early as the 1938–1939 Catalonian offensive in Spain’s civil war, the 8.8 cm guns had been towed into action behind the tanks, and it was estimated that over 90 per cent of their rounds were used against ground targets.

— Blitzkrieg by Len Deighton (Page 299 - 300)