Iran nuclear-era oil sanctions (2012)
The U.S. and EU imposed secondary sanctions on buyers of Iranian crude, threatening to cut them off from the U.S. financial system. Iran's oil exports fell from about 2.5 million barrels a day to under 1 million.
Iran's economy contracted, the currency devalued, and oil revenue collapsed.
The pressure brought Iran to the negotiating table, leading to the 2015 JCPOA nuclear deal.
Same secondary-sanctions mechanism is now used to isolate Iranian aviation, and it proved effective in forcing economic concessions.
