The impressive performance of the German 88mm FlaK series forced the US Army to consider adopting a similar weapon. The 90mm M1 cannon was designed in response; it is a dual-purpose artillery piece, capable of engaging both tanks and aircraft. The M1 line of 90mm guns has a number of variants, though the most common is the M2 with improved direct-fire capabilities and the M3 tank gun. The latter became the standard cannon of America's early MBTs. An effective weapon even in the modern day.