In the economic arena, the war ended the great depression. military spending that began in 1940 to bolster the defense effort gave the nation’s economy the boost it needed, and millions of unemployed americans returned to work to make the weapons of war needed to protect the united states. the renewed prosperity vindicated the theory of english economist john maynard keynes, who had earlier argued that sizable government spending could end a depression if the private sector was unable or unwilling to engage in such spending itself.