Enhanced security cooperation between Seoul and Tokyo would better protect South Korean, Japanese, and U.S. national interests in Asia. Both South Korea and Japan have extensive, highly capable militaries. Washington has strong relationships with both countries, but the third leg of the security triad—between Seoul and Tokyo—has been constrained due to bitter historic animosities and territorial disputes.

Why has the United States hesitated to impose the same legal measures against North Korea that it has already used with success against other countries for far less egregious violations of U.S. and international law?