As a tangent, pretty amazing the US never was able to build something equivalent to the ZSU-23. There was the Sergeant York project that ended in complete failure.
M247 Sgt York:
http://www.youtube.com/watch?v=TanFPsRaeto
All the more strange when you consider the best tank of WWII - the Russian T34 - was an American design (Christie).
Assad used the ZSU-23 with great effectiveness in the streets of Aleppo.