New Delhi, April 29 -- In this era of protectionism, defending globalization can feel like a losing proposition. But rather than retreat from the debate, it is more urgent than ever to spell out the costs of a trade war, which threatens to accelerate the fragmentation of the global economy because it is really a war on trade itself. To challenge the logic behind the US administration's protectionist agenda effectively, we must first understand it in clear and concrete terms.

The US tariff regime stands on four arguments. The first is that tariffs will boost government revenue and help reduce the US budget deficit, which many economists see as unsustainable. The Congressional Budget Office expects the federal deficit, currently at 6.4% of...