On December 26, 2011, in response to US, European, and potential Asian sanctions on Iranian oil exports, the government in Tehran issued a threat to “cut off the Strait of Hormuz.” The US Defense Department responded that any blockade of the strait would be met with force. On first read, it is easy to dismiss such saber rattling as another chapter in the new Cold War in the Middle East between Iran and its allies – including Syria, Hamas, and Hezbollah – and the US, Israel, and the Sunni Gulf States, mostly notably Saudi Arabia. Iran has since backed away from its threat, but the event still carries importance because it is unclear how both the US and Iran will continue to respond, particularly as the diplomatic and economic pressures grow more acute while Iran’s controversial nuclear program advances. Could such a verbal threat by Iran to cut off the Strait of Hormuz ignite a military conflagration in the region? By examining past episodes when countries issued threats to close oil transit chokepoints, this Policy Brief helps illuminate the dangers associated with the current crisis over the Strait of Hormuz.