Even earlier than that actually - the Greeks had both the differential gear and the steam engine.
There is pretty much nothing technological that would have prevented Athens from destroying its opponents with steam powered tanks several centuries B.C.
Plus at the time the standard tactic would be a deep phalanx, which would have been absolutely smashed by a tank driving over it.
I happen to host the blog (among others) of an author who has written just such a novel: Bring Laws and Gods. It should be released some time this year.
There is pretty much nothing technological that would have prevented Athens from destroying its opponents with steam powered tanks several centuries B.C.
Plus at the time the standard tactic would be a deep phalanx, which would have been absolutely smashed by a tank driving over it.