After much back-and-forth posturing by the Trump administration, book-ended by national security adviser John Bolton accelerating the planned deployments of an aircraft carrier battle group and a B-52 bomber task force to the Middle East, and President Trump commenting, “I hope not” when asked whether there would be a war, the American commander in chief threatened to destroy Iran on Sunday. “If Iran wants to fight,” Trump tweeted, “that will be the official end of Iran. Never threaten the United States again!”

Trying to pinpoint what prompted Trump to communicate what amounts to a genocidal threat is like reading tea leaves—more art than science. But after seeing his effort to isolate Iran diplomatically rejected by a united Europe, and learning from military leaders that a war with Iran would be far costlier and much more problematic than he originally thought, the president reverted to character, lashing out with apocalyptic fury against a nation that has frustrated his administration from its inception.

Trump has backed himself into a corner. The self-imagined dealmaker sincerely believed that by applying economic pressure on Iran, backed up with the threat of force, the Iranian government would come to the negotiation table and agree to a nuclear deal that denied it everything it had achieved through diplomacy with the Obama administration. Trump believed he could bully America’s allies in Europe to go along with him. And, in the end, when he asked his military leaders to provide him with options to forcefully compel Iran to bend to his will, Trump was told that nothing short of an all-out war, involving more than 500,000 troops, could provide the outcome he sought, and even then only at great cost. Trump had run on a platform that promised an end to costly wars of choice in Iraq, Syria and Afghanistan. If he pulled the trigger on Iran, his chances of reelection in 2020 would be all but eliminated.

The heart of Trump’s frustration lies with the military options he has been presented with, namely “OPLAN 1002.” Short for “operations plan,” OPLAN 1002 is the U.S. war plan for major military conflict in the Persian Gulf. If the current state of heightened tension with Iran were to explode into a military confrontation, it would be OPLAN 1002, or some iteration thereof, that U.S. military commanders would use to guide their operations, which could include neutralizing Iran’s nuclear infrastructure and securing the strategic Strait of Hormuz, through which about 18 million barrels of oil, which is 20% of global production, transits every day.

The issue of Iran’s nuclear capability has moved front and center after Trump’s fateful decision to withdraw from the Iranian nuclear deal last year and reimpose U.S. sanctions, including those on the sale of oil, Iran’s economic lifeblood. As a result, Iran has suspended certain aspects of the nuclear deal concerning the storage of heavy water and enriched uranium and is threatening to resume the enrichment of 20% enriched uranium, restart a heavy-water nuclear reactor and install advanced centrifuges. Moreover, if the U.S. moves to impede Iran’s ability to export oil, Iran has threatened to close the Strait of Hormuz to all traffic. For its part, the U.S. has promised to keep the Strait of Hormuz open through military action.

Vice Admiral Jim Malloy, commander of the U.S. Navy’s Bahrain-based Fifth Fleet, embodies the arrogance that infects senior American military leadership when it comes to the issue of securing the Strait of Hormuz. His command recently assumed operational control of the USS Abraham Lincoln carrier battle group, diverted to the Middle East as part of America’s military buildup against Iran. Addressing the question of whether the carrier battle group would remain in the Arabian Sea, where it currently operates, or if it would transit the strait and operate in the Persian Gulf, Malloy told reporters, “If I need to bring it inside the strait, I will do so. I’m not restricted in any way, I’m not challenged in any way, to operate her anywhere in the Middle East.”

Except he is, even if he won’t admit it. In the event of an all-out war with Iran, the USS Abraham Lincoln has about an 80% chance of survival while operating in the Arabian Sea provided its neither launching nor recovering aircraft at the time. (Iran could still locate and target the carrier group using its own surveillance assets and ballistic missiles, although the freedom of movement afforded by the Arabian Sea offers a measure of protection from attack.)

Operating inside the Persian Gulf is a whole different ballgame. Iran would overwhelm the Abraham Lincoln’s battle group with swarms of small boats, submarines, drones, cruise missiles and ballistic missiles, the carrier’s maneuverability and operational flexibility limited by its exposure to Iran’s lengthy coastline and the Gulf’s shallow waters. Such an operation would reduce the battle group’s odds of survival to about 20%; its chances of sustaining combat operations against Iran while operating in the Persian Gulf are virtually nil.

The vulnerability of the USS Abraham Lincoln and its eponymously named battle group is ultimately part and parcel of the larger issue of America’s ability to project military power in the region today. The threat posed by Iran’s military is unlike anything the U.S. has had to confront since the end of the Cold War; it most certainly has not faced anything like it in terms of sophistication and capacity during the 18-year global War on Terror that has dominated military planning since the terrorist attacks of 9/11. OPLAN 1002 was designed for a major military conflict involving modern combined arms operations. And yet, for the past two decades, the U.S. has been involved exclusively in low-intensity counterinsurgency warfare, fighting Al Qaeda and the Taliban in Afghanistan, as well as Shi’a militia, Sunni tribesmen and the Islamic State in both Iraq and Syria.

The U.S. Marine Corps, which bears the brunt of the responsibility for securing the Strait of Hormuz through its amphibious warfare capability, is no longer capable of conducting the kind of forcible entry operations required to fulfill this mission. In short, the requirements set forth by OPLAN 1002 are unattainable for much, if not all, of the U.S. military today. Any conflict with Iran based upon the assumptions and requirements set forth in OPLAN 1002 would most probably result in an American defeat brought about not by Iran prevailing militarily, but by the U.S. being unable to accomplish its objectives, leaving Iran intact and defiant.

OPLAN 1002 is a war plan that has been decades in the making. When I entered active duty with the Marine Corps in 1984, the U.S. had just transitioned from the Carter-era Rapid Deployment Joint Task Force, formed in 1980 to secure the Persian Gulf from a Soviet attack or subversion and insurrection conducted by a Soviet proxy or regional ally, to a dedicated combat command known as U.S. Central Command, or CENTCOM. I was assigned to the 7th Marine Amphibious Brigade, which operated as the Marine Corps component of the Rapid Deployment Force, in which my first assignment was to update the intelligence annex to OPLAN 1002. That summer, I participated in a major command post exercise conducted by I MAF (First Marine Amphibious Force), the higher headquarters for 7th MAB, in which we put OPLAN 1002 into practice, inserting (via a map-based study) a large Marine combat force into Iran for the purpose of moving inland and engaging an invading Soviet force.

Among the first things that struck me were the limitations on U.S. forcible entry capability. One of our planning assumptions was that Iran would be a passive partner in our operations, meaning we would be able to make entry to the port cities of Chah Bahar (on the Arabian Sea coast) and Bandar Abbas (astride the Strait of Hormuz) unopposed. In preparing the intelligence annex, I had noted it was highly unlikely the Iranians would behave in such a manner, and that we should be prepared to conduct full-scale forcible entry operations. The problem was that we didn’t have the capacity to project and sustain meaningful military power ashore in a contested environment, and even if we did, our combat power would be so depleted by dealing with the Iranian threat that there would be nothing left to confront an invading Soviet force. Since our mission was to deter Soviet aggression, we manufactured planning assumptions such as a passive Iranian host to make the exercise possible.

Even with the Iranians standing by, the logistical challenges of moving personnel and equipment ashore were astronomical. Simply put, we had to artificially slow down the Soviet advance, and limit Soviet interdiction operations, so we could off-load the ships. Even then, we ignored real-world issues such as narrow shipping lanes, congestion, lack of port facilities, etc. Had this been a real-world contingency, our shipping would have experienced a traffic jam into the Iranian ports that would have made them a sitting duck for any determined opponent; any sabotage or successful attack on the port itself would have made transitioning personnel, equipment and material from ship to shore impossible.

In August 1990, Iraq invaded Kuwait, and the U.S. was called upon to implement OPLAN 1002, this time in response to a regional threat in the Arabian Peninsula. In this iteration, however, the U.S. was able to make extensive (and exclusive) use of friendly Aerial and Sea Ports of Debarkation (i.e., airfields and ports under the control of friendly forces), which allowed for the uncontested and unimpeded flow of personnel and material into the Persian Gulf and ashore in Saudi Arabia. Even under these permissive conditions, it still took months to get enough combat power deployed into the Persian Gulf to make offensive operations feasible.

For the Marine Corps, and to a lesser extent the Navy, the battleplan adopted by General Norman Schwarzkopf, the commander of CENTCOM, was a disappointment. There would be no amphibious assaults against Iraq. Rather, two Marine divisions and accompanying Marine air wings would be deployed ashore in a manner that mimicked the employment of U.S. Army and Air Force assets. Moreover, the assignment given to the Marines—assaulting the teeth of the Iraqi defenses to “fix” them in place while the U.S. Army conducted a sweeping flanking operation—was considered suicidal. General Al Gray, the commandant of the Marine Corps, created a special “ad hoc study team,” reporting to Maj. Gen. Matthew Caulfield, the commander of the Marine Corps Warfighting Center, in Quantico, Virginia, to develop alternative courses of action for the employment of Marine combat units. Because of my experience with 7th MAB, I was assigned to the team as its intelligence officer.

After considering several options, the team settled on a bold division-sized amphibious assault on the Al Faw peninsula, which would advance inland and seize the Iraqi logistics hub of Az Zubair. One of the more innovative aspects of this plan, known by the code name “Operation Tiger,” was the employment of existing roll-on, roll-off (Ro-Ro) shipping as improvised causeways, allowing for the rapid transfer of combat-ready forces from ship to shore. This bypassed the need for the kind of port infrastructure usually required to offload a division-sized assault force. OPLAN 1002 called for a division-sized force being able to be projected ashore at D-Day plus 12 (i.e., 12 days after the initial assault); Operation Tiger envisioned a division-sized force ashore at D-Day plus one, with Az Zubair captured by D-Day plus 4.

While Operation Tiger received the enthusiastic endorsement of Caulfield, Gray and Headquarters Marine Corps, its unconventional approach to amphibious operations proved too much for Schwarzkopf and his CENTCOM planning staff, who were married to their operational concept. There would be no amphibious forcible entry operations during Operation Desert Storm. (As a footnote, I was approached by the chief of staff of CENTCOM Special Operations Command to adapt aspects of Operation Tiger so that Arab coalition forces could be rapidly moved into Kuwait City; concerns over Iraqi mines and casualties ended this effort as well.)

The next adaptation of OPLAN 1002 came in 2003, when U.S. forces were deployed to the Persian Gulf (again, using friendly aerial and seaports of debarkation in Kuwait) to participate in the invasion and subsequent occupation of Iraq. The forces deployed in support of the Iraqi invasion (192,000 U.S. forces, accompanied by 45,000 British and a few thousand other coalition forces) were considerably less than the 750,000 U.S. forces deployed during Operation Desert Storm. Even so, it took several months for these forces to be assembled and equipped for combat operations under permissive conditions. (Of note, the only amphibious assault conducted during the invasion was done by the British, who took four days to secure the Al Faw peninsula using two battalions of Royal Marines facing light resistance.)

Despite the massive size of its annual budget, the U.S. military today is but a shadow of its former self when it comes to amphibious operations. The U.S. Marines are not able to conduct brigade-sized forcible entry operations except under ad hoc conditions, and even then, only against a lightly held objective. Any notion of landing Marines on a contested shore in Iran is suicidal. And yet any plan to secure the Strait of Hormuz would require the seizure of Iranian-held islands located in the strait, the port city of Bandar Abbas, and the entire Iranian coastline along the strait inland to depths of up to 50 kilometers. This mission far exceeds the operational capacity and capability of the Marine Corps. Airpower alone cannot accomplish this objective either; as previously discussed, the U.S. aircraft carriers will be operating under duress, reducing effectiveness, and U.S. airbases in the region will be under near continuous Iranian ballistic missile attack, resulting in their closure or reduced effectiveness.

The biggest threat facing any U.S. force assembled in the region will come from Iran’s ballistic missiles. During the Gulf War, I was involved in the campaign to hunt down and destroy Iraqi ballistic missiles that were being fired at targets in Israel and the Arabian Peninsula. We enjoyed virtual air supremacy and were able to dedicate thousands of sorties in support of the counter-missile campaign. Special operations teams were inserted on the ground inside Iraq to assist in this effort. At the end of the day, not a single Iraqi missile launcher was destroyed by coalition forces. Today, in Yemen, the Houthi rebels use ballistic missiles to attack Saudi Arabian targets. Again, the Saudi Air Force, operating with total impunity (and supported by U.S. intelligence, which provides targeting support), has been unable to prevent the Houthi from launching missiles. Mobile relocatable targets such as the vehicle-mounted ballistic missiles employed by Iran will be virtually impossible to stop; any operation against Iran can anticipate continuous attacks from Iranian ballistic missiles for the duration of the conflict.

The version of OPLAN 1002 being discussed at the Pentagon today is a limited-scope operation involving some 120,000 troops. This force would have minimal forcible entry capability, and instead be geared toward conducting an air campaign designed to neutralize Iran’s nuclear infrastructure while securing the Strait of Hormuz; as such, most of the forces involved would be deployed to regional airbases and aboard U.S. Navy ships. As has already been discussed, this force will not be able to accomplish its mission of securing the Strait of Hormuz, which means that all oil shipments transiting the strait will be halted. Moreover, the Houthi drone attack against Saudi oil pumping stations (using Iranian drones) has shown that the totality of the oil-producing infrastructure in the region is vulnerable to interdiction. As such, any military operation against Iran will result in the near total shutdown of oil exportation from the Gulf Arab states, which will have a devastating impact on the economy of the U.S., Europe and the rest of the world.

This modified OPLAN 1002 will most likely make heavy use of airpower, including both air- and sea-launched cruise missiles. While the U.S. can launch several hundred cruise missiles a day against Iranian targets, this number is virtually meaningless. Iran has spent decades preparing for a war with the U.S. and has studied American weaponry to a degree that is perhaps unappreciated in the West. Iran has in its possession intact examples of U.S. cruise missiles recovered from battlefields in Syria, Iraq and Afghanistan (as well as from scores of missiles that flew off course and landed on Iranian soil.) Russia has shared with Iran radar and electronic intelligence on the U.S. cruise missiles, and Iran’s air defenses are prepared to engage. Likewise, Iran has been carefully monitoring U.S. air operations in Afghanistan, Iraq and Syria and has collected similarly in-depth intelligence on U.S. aircraft and air-delivered munitions. The successful Iranian operation to hijack an American RQ-170 stealth drone over Afghanistan and divert it to Iran, where it was taken under control and reverse-engineered by Iranian scientists, stands as an example of Iran’s capabilities in this regard.

It will take the U.S. weeks, if not months, to deploy enough air power into the region to sustain a meaningful air campaign against Iran. During this time, Iran will disperse its forces to remote sites, many of which are underground and impervious to attack. U.S. cruise missiles, costing some $1.4 million each, will be destroying empty buildings, while U.S. aircraft will have to fly in contested airspace for the first time this century, decreasing operational efficiency while suffering casualties in terms of downed aircraft and aircrew that could very well prove to be unsustainable. Any attempt to militarily engage Iran with a force level of 120,000 troops would be sheer folly and doomed to fail. This does not mean Iran will escape destruction—far from it. U.S. aircraft will reach their targets, and U.S. munitions will be employed with great effect. Iran’s civil and industrial infrastructure will be devastated, and tens of thousands of Iranian civilians would be killed. But the U.S. air campaign will not defeat the Iranian military, which will not only defend Iranian territory but also strike out against U.S. forces in the Persian Gulf region, as well as military and industrial targets, including oil and gas infrastructure, of any nation providing assistance to the American war effort.

The bottom line is that any military engagement of Iran based upon the force structure supported by the 120,000-troop figure cited by the media cannot, and will not, result in a victory for the United States. Moreover, by initiating an armed conflict with such limited resources, the U.S. could very well be setting itself up for defeat. Iran has the capability to sink U.S. naval vessels, shoot down U.S. aircraft and destroy airbases supporting U.S. air operations. Iranian-backed militias in Syria and Iraq could very easily overrun U.S. military bases in those two countries, annihilating the garrisons based there. U.S. airpower that would normally be employed to defend these garrisons would be tied down in supporting operations over Iran.

President Trump has dismissed the reports citing the plan to deploy 120,000 U.S. troops to the Persian Gulf as “fake news,” noting that if he were to engage Iran militarily, he would use “a hell of a lot more troops than that.” This is closer to the truth. OPLAN 1002, in its current iteration (which is derived from realistic calculations regarding actual force availability), probably envisions up to 500,000 U.S. troops for any full-scale war with Iran. This number would support an actual invasion of Iran, which would probably be conducted from bases in Azerbaijan and from a beachhead established at Chah Bahar, on the coast of the Arabian Sea.

There are three major problems with any “massive intervention” operation against Iran. First and foremost, it would effectively denude U.S. forces worldwide, meaning the U.S. would lack any meaningful military capacity to respond to crises in Europe or the Pacific. Second, it would require significant regional support, including from Turkey, Georgia and Azerbaijan, which is highly problematic. Even here there would be no guarantee of an American victory. Iran was behind the successful resistance of Hezbollah against Israel in August 2006, and there is every reason to believe Iran has prepared a defense designed to lure any invading force deep into its territory, and then cut it off and destroy it. While the defeat of the U.S. military on the battlefield is an unlikely outcome, denying the U.S. an outright victory is a distinct possibility.

This is the reality that confronts Trump as he wrestles with the consequences of his hyper-aggressive policy posture toward Iran. Having embraced a policy of “maximum pressure” designed to compel Iran into foregoing its nuclear program, Trump is now confronted with the harsh fact his policy has failed, and the consequences of this failure could very well mean an Iran with increased nuclear capability, with the U.S. unable to build a coalition capable of reining it in. Trump has, for the moment, put the brakes on any precipitous rush toward war with Iran, instructing the Defense Department not to provoke a confrontation. However, he still must deal with European anger over the U.S. policy of economic sanctions targeting Iran and the detrimental impact of his decision to withdraw from the Iran nuclear deal.

In the spring of 2018, Trump ignored the advice of his then-secretary of state, Rex Tillerson, and then-national security adviser H.R. McMaster to stick with the Iran nuclear deal. Instead, he replaced both with Mike Pompeo and John Bolton respectively, each of whom advised Trump to withdraw from that agreement, thereby setting the U.S. on its current policy course regarding Iran. Trump ran for president on a platform he would not only get the U.S. out of its seemingly endless wars in Iraq and Afghanistan but avoid any similar misadventures. He could easily be facing Joe Biden in the 2020 election, and the last thing he wants to do is offset the former vice president’s politically damaging support for the Iraq war by getting the U.S. bogged down in a similarly disastrous conflict in Iran—especially one so clearly a product of Trump’s own political miscalculations.

There remains the possibility Trump will back away from his threat to eliminate Iran as a nation state and instead focus his efforts on sustaining the current economic boom upon which his bid for reelection hinges. Iran is not looking for a fight, but neither is it willing to accede to the unrealistic demands placed on it by the Trump administration regarding its nuclear program and regional presence. By raising the specter of an all-or-nothing confrontation, however, Trump is creating the conditions for a self-fulfilling prophecy, one in which he will get the war he claims not to want while costing him the second term he claims he does. But the demise of Donald Trump’s political ambition is the least of the casualties of such a policy. A war with Iran will cost America tens of thousands of casualties, while killing or wounding hundreds of thousands of Iranians. Any U.S. victory would be pyrrhic in nature, crippling the U.S. and global economies while further diminishing America’s already diminished position in the world.

But, perhaps most important, it would be a war that, if America’s experience with OPLAN 1002 tells us anything, we may not win—at least not in a conventional sense. The prospect of an American invasion force stalled in the deserts of Iran, surrounded by a hostile population and under continuous attack, is very real, and meets the “extreme circumstances to defend the vital interests of the United States, its allies and partners” threshold for the employment of nuclear weapons as set forth in the 2018 Nuclear Posture Review published by the Department of Defense.

It is this reality that may have prompted Trump’s threat to “end” Iran—a madman’s lashing out in frustration at a world that refuses to behave as he desires, and therefore must be destroyed as a result.