Responses to an article in the “At the Brink” series, raising doubts about a huge overhaul of U.S. nuclear capacity.

Iran’s supreme leader faces a critical choice: whether to pursue nuclear weapons.

The sales of intelligence agency data raised awkward questions as the nation is expanding military information sharing with the United States.

In a classified document approved in March, the president ordered U.S. forces to prepare for possible coordinated nuclear confrontations with Russia, China and North Korea.