A nuclear strike on Iran is a real possibility, and it would most likely come from Israel — a dangerous turn for the whole region.

• Israel is seen as the side most likely to use a nuclear weapon against Iran, not the other way around.
• The main reason Israel hasn't done it yet is fear of the fallout — other countries reacting and the world turning against it.
• Iran isn't the only danger; other nuclear-armed states like Pakistan could get pulled in, so any strike might not stay one-sided.
• It would be the first use of nuclear weapons in war in 80 years, breaking a line held since 1945.

Outlook: Expect more nuclear threats and brinkmanship, with the risk of an actual strike rising if Israel believes it can avoid the consequences.