Intelligence collected by the U.S. government shows Iran’s leaders believe the U.S. planned to attack them, prompting preparation by Tehran for possible counterstrikes, according to one interpretation of the information, people familiar with the matter said.

That view of the intelligence could help explain why Iranian forces and their allies took action that was seen as threatening to U.S. forces in Iraq and elsewhere, prompting a U.S. military buildup in the Persian Gulf region and a drawdown of U.S. diplomats in Iraq.

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