One of the most legendary war scenes ever made was the attack in Paths of Glory. For that, Kubrick found a retired German major from the Great War who had experienced the real thing, who drilled the extras into authentic behavior.
All that was needed here is accurate CGI--guys looking at a monitor.
*John Huston to Robert Mitchum: Kid, we can make a good movie or a bad movie. Producer wants it bad, we can make it bad. Cost 'em more, but we can make it.