The literal answer to your question is deficit spending, financed through borrowing. War is the proper mindset. If your country goes to war, what matters is th

The literal answer to your question is deficit spending, financed through borrowing. War is the proper mindset. If your country goes to war, what matters is the number of factories you have that can produce tanks and airplanes and guns. You worry about your soldiers running out of ammo or your cities being bombed, not higher prices next year due to borrowing-driven inflation. What matters is real resources. We are all going to pay for this horrible luck one way or another: through direct payments, or unemployment benefits, or worst case - pounds and pounds of flesh.