It seems a bit strange to say that the ruling classes would pay workers more to support a war. Another possibility is that war decimates the return of capital because speculative investments fail due to instability, but basic and well established needs (the "real" economy") still get funded because people still want to eat.
You ignore the destruction of capital war causes. Germany in 1945 had maybe three bricks still stacked on top of each other, but had lost less than 20% of its prewar population.
