We need to dispel the illusion that cuts to the national security budget really save us money. Some Republicans who oppose compromising on taxes make the same miscalculation as Democrats who favor deeper defense cuts. They think that if the United States would simply scale back its role in the world, it could save money and make raising further revenue unnecessary. This is a faulty assumption. The present global economic and political order, which has provided the environment in which the United States has grown and prospered for decades, is built on and around American power and influence. Were the United States to cease playing its role in upholding this order, were we to retreat from East Asia or to back away from the challenge posed by a nuclear Iran, the result could only be global instability. From a purely economic perspective, it would be far more costly to restore order and stability — both essential to a prosperous global economy — than it would be to sustain it. Indeed, if there is no deal on the fiscal cliff and the long-term fiscal crisis because Republicans and Democrats won’t make a sensible compromise on raising revenue and reforming entitlements, and the result is further cuts in the defense and foreign affairs budgets, then the cost — including the dollar cost — could make the present budget arguments look absurdly petty.

The point is, none of the elements of a deal to address the fiscal crisis — not taxes or entitlements or anything else — can be considered in isolation. We should have learned the lesson of the 1920s and 1930s, another period when a global economic crisis was inconveniently accompanied by an unsettled and dangerous geopolitical situation. Then, American leaders concentrated on trying to address their domestic economic problems, somehow imagining these could be separated from the broader international economic and political environment. The United States actively retreated from global involvement to focus on what these days we would call “nation-building at home.” The result was disastrous both at home and abroad.