At the start of the series Lansky was still a teenager. And weren't him and Luciano too young (in season 1) to be hanging with Rothstein and going to the meetings with him?

I know that Rothstein was involved in those rackets, but being a gangster means being part of some gang or mafia-like organization, ie. being part of a crew. Rothstein had no manpower behind him and yet he talks about "waging a war". With what 'army'? Not to mention him threatening Frankie Yale.

As far as I know blacks weren't involved in major bootlegging operations. Were there ever any real major gang wars between blacks and the mafia? I don't think so, but I could be wrong of course.