First, it is an argument for international isolation, for in a time of war, there is no industry that does not contribute to national defense. Second, if the case is made for boosting the output of a strategic industry—say aerospace—it is more efficient to achieve this outcome with a subsidy financed out of taxes than with a tariff or import quota. A subsidy would keep the industry operating at the scale that is judged appropriate, and free international trade would keep the prices faced by consumers at their world market levels.