Hello there! World War I caused a massive spike in military spending- 22% of the GDP. Following the war, military spending fell dramatically to 1-2% in the 1920s and 3-4% in the 1930s. This pattern of heavy spending in wartime and extremely low spending in peace stopped following World War II when the US began spending a minimum of 3-5% from the 1950s to present, with wartime spikes. Information from Census Bureau’s Historical Statistics of the United States: From Colonial Times to 1970, pages 38-50 and USGovernmentSpending.com, which was surprisingly well sourced.