4.5 million? During the 18 days of the battle of Kurukshetra, more than 650 million people died. Moreover, there were only Kshatriyas (warriors - individuals for whom shame is worse than death); there wasn't a single Vaishya (merchant) or Shudra (worker). There were also Brahmins present.
In this battle, seismic, bacteriological, nuclear, elemental, and psychic weapons, among many others, were used.