That one of these potential adversaries would launch a bolt-from-the blue, all-out attack against a U.S. ally seems much less likely than such limited aggression. It is hard to imagine a major Chinese invasion of the main islands of Japan or the metropolitan area of Seoul in South Korea, for example. And for all of Vladimir Putin’s recent adventurism, the forcible annexation of an entire NATO country, even a small Baltic state, strikes most as implausible. Such attacks, even if initially successful, would and should risk massive responses by the United States and its allies.3 President Donald Trump’s tepid support for NATO, and for U.S. alliances in general, may muddy the deterrence waters somewhat. But even under his presidency, U.S. alliance commitments remain formally in place and American troops remain forward deployed from Korea and Japan to the Baltics and Poland. It would amount to a huge roll of the dice for an aggressor to seek to conquer any one of these states. To be sure, U.S. defense policy should continue to display resoluteness and create capacities of the type needed to deter such large-scale attacks, not just wishfully assume them away. But on balance, deterrence failure on such a massive scale seems very unlikely. Strong American-led alliances, conventional and nuclear deterrence, and economic interdependence all militate strongly against any conscious decision by an adversary to initiate large-scale war.
