Between tweets about migrants, the economy, and Democrats who are running for president, President Donald Trump on Sunday spared one tweet on the rising tensions between the United States and Iran.

“If Iran wants to fight, that will be the official end of Iran. Never threaten the United States again!” he said.

If Iran wants to fight, that will be the official end of Iran. Never threaten the United States again!

— Donald J. Trump () May 19, 2019

While observers are hoping the increasingly hawkish talk from both sides is simply political bellicosity rather than actual military threats, it’s hard to ignore threats to bring an “official end” to a country of over 80 million people.

Tensions have increased exponentially since National Security Adviser John Bolton framed the routine deployment of a U.S. carrier to the Persian Gulf as a military escalation in early May. Since then, there has been a volley of confusing claims from the Trump administration, including claims of a heightened threat from Iranian proxies in Iraq, without providing any specification.

Iran’s leaders responded by asking the militias they support to prepare for a proxy war, possibly in response to what they see as U.S. military threats.

What would war with, on, or against Iran — distinctions that signal varying types of military engagement — look like? What kind of troop deployment, timeline, civilian and military casualties on both sides, and expense are we talking about?

The 2003 invasion of Iraq has cost the United States more than $1 trillion, in addition to the deaths of at least 4,887 U.S. troops and at least 206,000 Iraqi civilians.

Of course, the nature of these questions is speculative — war is not as predictable as dominoes. There are dynamic events that can change the entire course of a conflict. As of now, the numbers rest somewhere between Sen. Tom Cotton’s (R-AR) “two strikes” estimate and a total apocalypse.

Gil Barndollar, director of Middle East Studies at the Center for the National Interest, who served as an infantry officer in the U.S. Marine Corps in both Afghanistan and the Persian Gulf, told ThinkProgress that even if the United States were to assume “completely permissive conditions” from Iran (no missiles, chemical, or biological attacks, etc.), it would still take “months to mobilize and stage forces” for such an operation.

“The entire active duty U.S. Army and Marine Corps today totals a bit over 600,000 troops. That is not enough men to invade Iran. Even if you mobilized the entire National Guard and Reserves, you would not feel comfortable invading Iran with a force that size,” he said, adding that it’s hard to speculate about casualties and costs. What would be needed for sure, though, is a draft.

Barndollar, who answered questions via email, said the two main factors to consider are Iran’s size and “hellacious military geography,” which he said, could be used as part of the country’s strategy to “eat up invading forces piecemeal.”

Iran’s population is over twice that of Iraq or Afghanistan, and its landmass is almost as large as Western Europe. Barndollar, who was deployed twice to neighboring Afghanistan, notes that Iran “is bordered by mountains on three sides and the sea on a fourth.”

A land invasion would require that a neighboring country allow access to its border, and of this, said Barndollar, “There is little chance.” Even Iraq, where the United States currently has just over 5,000 troops, has made its position on this clear: It won’t be used as turf for a proxy war with Iran.

And when it comes to the fourth border, at the Persian Gulf, Barndollar said, “An amphibious landing would be even more fraught with risk.”

“The Navy would be hard-pressed to muster enough amphibious assault ships to get even one Marine Expeditionary Brigade to the fight [with] only about 15,000 troops,” he said.

This means the merchant marine ships would have to bring in the bulk of the force, something for which they are not prepared.

This fleet would also catch a lot of fire from Iran. “Missiles, mines, Missiles, submarines, and fast attack boats — suicide boats among them — would pose enormous threats to U.S. ships,” lists Barndollar.

Nuclear targets?

Air strikes would have to be part of this operation, but the sheer number of targets would mean that the United States would likely run out of precision-guided munitions.

Would any of those airstrikes target Iran’s nuclear energy facilities? Iran’s nuclear program has, after all, been at the center of the Trump administration’s stated acrimony with Iran. The president pulled the United States out of a 2015 nuclear deal (the Joint Comprehensive Plans of Action, or JCPOA), which saw Iran getting sanctions relief in exchange for curtailing its nuclear enrichment program.

But Russia, China, France, the United Kingdom, and Germany remain committed to the deal, and Iran’s nuclear program continues under inspection from the U.N.’s nuclear watchdog agency. (It’s unclear whether news that the country is increasing its production of low-enriched uranium will violate the terms of that deal.) Iran’s nuclear reactors were considered targets last summer, shortly after the United States left the JCPOA and started reimposing sanctions on Iran.

Daryl Kimball, executive director of the Arms Control Association, said that while both the United States and Israel had the conventional weapons capabilities to launch airstrikes, some of these facilities are underground, so it’s unclear how much damage could be done with such airstrikes.

“But I’d like to emphasize that we have succeeded through diplomacy, and through the JCPOA, to limit Iran’s capacity to produce just enough material for just one [nuclear] bomb in a twelve-month span. And then it still needs to assemble the bomb, it has to figure out how to deliver that bomb. So Iran is years away, at worst, of posing any kind of nuclear threat to the United States,” he said.

Any discussion of striking those facilities is “out of line with the current threat environment,” said Kimball.

But given that Trump said over the weekend that Iran would essentially cease to exist, it’s important to consider the possibility of a nuclear strike — something Kimball didn’t even want to think about.

“Any nuclear conflict, even if it involved just a relatively small number of relatively lower-yield weapons, as in Hiroshima-sized city-busting weapons would produce catastrophic effects,” he said.

The worry, though, is that in the high-traffic (oil tankers and military presence) pressure-cooker that is the Persian Gulf right now, things could inadvertently go wrong.

“Iran is not pushing for a fight against the U.S., but a conflict in Iran in the Persian Gulf region right now,” said Kimball, “the chances for that are higher because of the possibility of a miscalculation by one side or the other, and the escalation of a small incident to a larger conflict.”