U.S. Secretary of Defense James Mattis has wrapped up his first visit overseas in his new job, a trip that took him to South Korea and Japan. Mattis provided calming reassurance in both countries, reaffirming the U.S. commitment to both allies and the priority the Trump administration gives to Northeast Asia. Mattis' message is vitally important as the world focuses on the spectacle that is President Donald Trump; it must not overlook the signals of continuity in U.S. foreign and security policy.

While Trump as a candidate said many things that troubled allies and encouraged adversaries, since taking office, his administration's statements about alliances in Asia have hewed closely to traditional policy of the United States. The decision to send Mattis to Asia on his first overseas journey as defense secretary is a clear sign that those allies retain a singular importance in U.S. thinking, a message that he reinforced in both countries.

In South Korea, Mattis was blunt. After meeting South Korean Defense Minister Han Min-koo, he pledged that "Any attack on the United States or on our allies will be defeated and any use of nuclear weapons will be met with a response that will be effective and overwhelming."