This has not been on Iran's list prior to yesterday, and Donald Trump, the U.S. president, has told other ruling classes to head to the waterway and just take the Strait of Hormuz.

Trump Threatens to Take Tehran's Oil as Iran Says U.S. Proposal Is "Unrealistic"

The narrow waterway through which a fifth of the world's oil and liquefied natural gas (LNG) ordinarily passes has emerged as the Islamic Republic's most potent weapon. And it is now seeking to turn into both a source of potentially billions of dollars in annual revenue and a pressure point on the global economy, according to a report by CNN. 

Iran has long threatened to close the Strait in case of an attack. So far, few political analysts actually expected it to follow through, or for it to prove so effective in disrupting global trade flows. The scale of the impact appears to have expanded Tehran's ambitions, with the new demands suggesting it is seeking to turn that leverage into something more durable.