And I saw heaven opened, and behold, a white horse, and he that sat upon him was called faithful and true, and in righteousness he doth judge and make war. (Rev. 19.11)
James Durham's comments on this text (Commentary on Revelation, p. 890) are worthy of consideration by magistrates who must decide whether and how to manage war justly:
And then, secondly, it is added, that in righteousness he doth judge and make war: which implieth, that there is a right end in His undertaking, a right cause, and a right manner of proceeding in it.