It absolutely does. If China, e.g., invaded your country, fighting back would not be just?
God told Israel to START wars with its neighbors because He'd had enough with those pagan populations. But, they had to slaughter tons of people -- including children. Not pretty, not desirable, but like radical surgery, sometimes war is necessary.
"War is not 'the best way of settling differences, it is the only way of preventing their being settled for you." (G.K. Chesterton)