Forty years ago, the U.S. made the mistake of not knowing about the deteriorating health of Mohammad Reza Shah Pahlavi. Failure to know that the shah was dying from cancer led to blunders in American policy, causing Washington to engage in a diplomatic course that did little to keep its staunch ally from being overthrown and replaced by a regime that has remained implacably hostile to the U.S. ever since. Prior behavior indicates that, had it known of the shah’s condition, the United States might have moved more aggressively to stabilize his health and keep him in power, a move that would have had dramatically different consequences for the United States.

It is therefore crucial that American intelligence have a good sense of Khamenei’s condition, lest American policymakers be surprised again in a critically important strategic region.

In 1979, the shah’s cancer played a critical role in his decision to capitulate to his opponents’ demands that he depart from Iran, a seminal moment in the course of the Islamic Revolution. It caught the American political establishment off guard. They had not anticipated that Iran’s paramount ruler would buckle while he still maintained the support of the country’s sizable military and security apparatuses. It also had cataclysmic consequences for the United States: the establishment of anti-American Shiite theocracy at the helm of the Iranian government.