What did Donald Trump do today?

He threatened Iran with the same economic consequences they've lived with for decades.

In a post to his private microblogging page today, Trump announced the "MOST CRUSHING ECONOMIC OPERATION EVER" against Iran, adding that "ANY country that allows its financial institutions, businesses, airports, or government entities to provide any type of lifeline to Iran will itself face TREMENDOUS Economic Consequences."

Presumably, Trump didn't mean the United States, although that is the only country to meaningfully relax its sanctions against Iran in the past year. Trump, who quickly became desperate to mitigate the economic consequences of starting a war in the Persian Gulf, was forced into the absurd situation of making it easier for Iran to sell oil in the middle of a war, thus effectively helping to fund its military response.

Trump's message didn't name individual countries, saying only that "You know who you are." That's true—who Iran does business with is something everyone knows. Its largest trading partner is China, which Trump cannot meaningfully threaten with sanctions. Iran also does considerable business with Russia, often in the form of trading oil for weapons that are then used against the United States. Trump has always been extremely reluctant to take action against Russia due to his personal entanglement with the Putin regime. 

Another major trading partner for Iran is North Korea, which has never obeyed international sanctions and is not likely to start now. Trump believes he has a personal friendship with North Korean leader Kim Jong-un, and effusively praises him in public. 

It's not clear whether there is even anything Trump can do to make sanctions more "CRUSHING" than they already were. Iran has been under extraordinary international sanctions for most of the last 40 years, with the only partial relief coming during the era of the JCPOA. That was the international agreement that successfully kept Iran from refining any weapons-grade nuclear fuel, until Trump pulled the United States out of it in 2018. Countries like China only ever paid lip service to those sanctions, while US allies were already complying with them.

Trump's saber-rattling comes immediately after the United Arab Emirates, Iran's second-largest trading partner, abruptly cut off trade in response to an apparent Iranian attack. That really will put some economic pressure on Iran, which has denied that it launched any attack at the UAE.

Why does this matter?

• Empty threats, whether or not they're tweeted in all caps, only show weakness.

• There's lack of leadership, and then there's letting a tiny oil kingdom do the hard work of managing world affairs for you.