US military planners are reportedly weighing the first use of nuclear weapons against Iran, a dangerous shift that alarms senior officers and raises the risk of a far wider war.

• Internal discussions are said to include striking first with nuclear weapons rather than only using them in response.
• A revised nuclear doctrine lowers the bar for when such weapons can be used.
• The main reason is practical: America has burned through its stock of ordinary bombs and missiles, and has plenty of small nuclear ones sitting in storage.
• Top uniformed officers are described as frightened by the direction of the talks.
• Almost no one in Congress is pushing back or warning Trump away from the idea.

Outlook: Expect pressure to build for someone in Washington to publicly rule out first use, but with Congress silent, the lower nuclear threshold stands.