A report by the House Armed Services Committee’s majority staff estimates that this would cut the Army and Marine Corps from 771,400 personnel today to 571,000. The Navy would go down from 288 ships to just 238. The Air Force would shrink from 1,739 fighters to 1,512 and from 118 bombers to 101. But perhaps the biggest worry is what these cuts would mean for research and development, currently just 11 percent of the Pentagon budget.

Now, it may be that we are entering a period of unprecedented peace and brotherly love. Maybe the Arabs will live happily ever after with new democratically elected leaders. And maybe the Chinese will always be our buddies. But I would not like to bet $492 billion on that. The future I fear is the one that comes after most big financial crises: a period of populist anger, political instability, and cross-border conflict. The youth bubble in the Greater Middle East is at its peak. Resource wars are looming as emerging-market demand outstrips supplies of everything from rare earths to fresh water. And China is already a credible threat to our cybersecurity.

I worry that our national-security strategy is currently being improvised in response to fiscal and domestic political pressures rather than to rational risk assessment. And I remember the old Latin adage: Si vis pacem, para bellum—if you want peace, prepare for war.