Lanchester designed his square law for modern warfare and, without question, the vast majority of interest has focused on that category of equations. But it's his linear law that is most relevant to the evolution of extreme weapons. By contrasting ancient and modern warfare, Lanchester helped define the circumstances in which large weapons will, and will not, be cost-effective. When opponents can concentrate their fire—gang up on an opponent simultaneously—investing in large weapons is probably a mistake. On the other hand, when soldiers duel each other at close range, face-to-face and one-on-one, then the better fighter is likely to win. Because fighting ability often depends on the size of a weapon, duels can lead to situations where bigger and bigger weapons prevail.

Emlen, Douglas J, Animal Weapons_ The Evoluti…, loc. 238