The alliance is bolstering its military deterrent in Europe amid Russia’s invasion of Ukraine and has expanded to include Finland and Sweden.

China is North Korea’s biggest trade partner and has leverage over Kim Jong-un’s regime, yet its policies focus more on border stability than nuclear threat.

The U.S. government responds to scores of disasters each year in coordination with foreign, state, and local partners, but more frequent and severe storms, fires, and floods are straining resources.

President Donald J. Trump has wide latitude to enact the sweeping changes to U.S. foreign policy that he has promised, but his executive authority is constrained by congressional legislation, treaty …