WASHINGTON, D.C.: US Defense Secretary Jim Mattis spent four days in East Asia trying to keep on the rails key relationships -- two friendly, one adversarial -- that his boss President Donald Trump has thrown into confusion.

It's now a familiar role for the Pentagon chief, not just in Asia but across Europe and the Middle East. With Trump disrupting one relationship after another, provoking rivals and unnerving friends, Mattis is the one making sure they can still work on their traditional foundations.