It all starts with $1.7 billion the U.S. Treasury transferred to Iran’s Central Bank in January, during a delicate prisoner swap and the implementation of last summer’s nuclear deal to resolve a long-standing dispute about Iran’s arms purchases before the revolution of 1979.

For months it was unclear what Iran’s government would do with this money. But last month the mystery was solved when Iran’s Guardian Council approved the government’s 2017 budget that instructed Iran’s Central Bank to transfer the $1.7 billion to the military.

Saeed Ghasseminejad, an associate fellow at the Foundation for Defense of Democracies, spotted the budget item. He told me the development was widely reported in Iran by numerous sources including the state-funded news services. “Article 22 of the budget for 2017 says the Central Bank is required to give the money from the legal settlement of Iran’s pre- and post-revolutionary arms sales of up to $1.7 billion to the defense budget,” he said.