It is not just that John is killed and Mark crippled for the rest of his life, while Paul returns home safe and sound and enjoys all the privileges accorded to veterans. But it would be foolish to deny that the profit system produces the best weapons. The most important thing in war is not to avoid the emergence of high profits, but to give the best equipment to one's own country's soldiers and sailors. The worst enemies of a nation are those malicious demagogues who would give their envy precedence over the vital interests of their nation's cause. Of course, in the long run war and the preservation of the market economy are incompatible.
Capitalism is essentially a scheme for peaceful nations.
But this does not mean that a nation which is forced to repel foreign aggressors must substitute government control for private enterprise. If it were to do this, it would deprive itself of the most efficient means of defense. There is no record of a socialist nation which defeated a capitalist nation. In spite of their much glorified war socialism, the Germans were defeated in both World Wars. What the incompatibility of war and capitalism really means is that war and high civilization are incompatible.