Sixty-three years ago, a (possibly amphetamine-addled) British Prime Minister, Anthony Eden, launched a military attack against a Middle Eastern country with the goal of provoking unrest that would topple its troublesome leader. Eden had conspired with others to create the pretext for the military attack. In the last days of October 1956, they swung into action.

In military terms, the attack went as planned. But politically — strategically — it was a fiasco. Egypt’s Gamal Abdel-Nasser, the conspirators’ target, stayed in power and died in office in 1970. Eden’s fate was less happy. By early January 1957 the U.N. had forced him to pull out all the troops he’d sent into Egypt and, as Britain’s economy and finances tanked, his irate colleagues in the Conservative Party toppled him. He never came back.

Eden’s disastrous adventure in Egypt in 1956 is not completely analogous to what we might expect if President Trump and his cabinet should launch a military attack against Iran. But there are enough good lessons from the 1956 Suez Crisis that it is worth examining it closely, so we can understand in what ways a U.S. attack on Iran might be similar to Eden’s Suez fiasco, and in what ways different.

What is undoubtedly the same about both crises is that they have (or would have, in the case of a still-hypothetical U.S. attack on Iran) broad effects on the international system far beyond the Middle East — including a massive, possibly very rapid, diminution in the global power and standing of the Western attacking power.

In the 1956 Suez Crisis, within hours after Eden and his co-conspirators in France and Israel had launched their assault on Egypt, they learned that President Dwight Eisenhower was strongly opposed to it. And Eisenhower acted swiftly force them to halt and reverse their plan. He used hardball to bend them to his will: not just a strong resolution passed in the United Nations, under a special procedure used to sidestep Britain and France’s veto in the Security Council, but also swift U.S. steps to undermine the British pound.

Eisenhower’s speedy intervention halted the assault on Egypt in its tracks. Within just a few months all three of the aggressing powers had withdrawn their troops, ceding the areas of Egypt they had occupied to the U.N.’s first-ever peacekeeping force.

Eisenhower’s intervention also had broad, long-lasting effects for the British Empire. Britain, like France, had already been badly weakened by World War 2. In 1947, London had been forced to “give” India its independence and to hand the ever-troublesome Palestine Question to the United Nations. But in 1956, many members of the British elite still harbored dreams of imperial grandeur.

After Suez, they realized they could neither deny Washington’s leadership nor defy its diktats.

A new realism took hold. British defense planners started planning to roll up the long string of military bases they had long maintained “East of Suez.” In 1970, Qatar, Bahrain, and the seven princedoms of the United Arab Emirates gained independence as the British dismantled the military outposts they had long maintained there. British diplomats negotiated new futures for previous imperial strongholds in Aden and Hong Kong. Throughout those years, former colonies throughout Africa were also gaining independence. A new wave of leaders in London, from both parties, started seeking a new future for Britain as a part of Europe, rather than head of its own global empire.

As for the United States, after Suez Washington’s international stature went up significantly — especially among the “Non-Aligned” nations of the Global South, many of whose leaders then judged the United States to be significantly different from the European colonial countries whose rule they had suffered from so grievously.

So in 2019, we can certainly expect that any U.S. attack on Iran would also have wide global reverberations — and all the more so if such an attack is launched (as was the attack that Eden and his allies launched in 1956) in the absence of any clearly proven prior attack to which it is demonstrably a “response.”

The similarities between the two situations include:

• The possibly unsettled mental state of the Western protagonist at the time (Eden, Trump.)
• The protagonist (or in 1956, coalition of protagonists) knowing it enjoys strong military superiority over the government being targeted.
• The location of this crisis in the Middle East, a region with special geopolitical characteristics.
• The strong instigatory/provocative role of “local” allies in the region.
• Freedom of international waterways being a factor (or even a possible casus belli.)

These similarities are striking, and not trivial. But there are significant differences between the two situations, too. They include differences in the shape of the international power balance and, to some extent, in the tools available to any potential “constraining” power.

Back in 1956, most of the world system was clearly divided between the two big camps of the Cold War. That duopoly and the situation of reciprocal nuclear terror (“mutually assured destruction”) between the camps imposed a certain discipline on the international system. In 1956, one of Eisenhower’s main motivations for acting fast to reverse the aggressive acts of his two European allies had, after all, been that at that same exact time he was trying to win international condemnation of the Warsaw Pact’s recent aggression against Hungary.

And in 1956, there was an Eisenhower: that is, a strategically smart leader in a country that was muscular enough to swiftly impose its discipline on numerous other powers, including its own wayward allies.

Today, if Trump should launch an aggression against Iran, what other government or coalition of governments would be both able and willing to exert a similar restraining role over the United States?

In 1956, Eisenhower imposed his will on the British, French, and Israelis primarily through the use of two significant levers of “soft” power. One was the legitimating role of the United Nations (and the wiliness of his diplomats in winning a “Uniting for Peace” resolution that allowed the U.N. to take decisive action that sidestepped the British and French vetoes in the Security Council.) The other was the United States’ raw power in the global financial system. Before the Suez Crisis, the U.S. Treasury underwrote the pound sterling. Once the invasion started, that backstop was pulled away. The pound, which had been under great stress since the depletions of World War 2, instantly threatened to collapse.

In the current U.S.-Iran standoff, the shape and dynamic of the global power balance are both notably different than in 1956. There is no global duopoly to impose structure and discipline on the system. And there is no single, basically friendly country with a very strong economy waiting in the wings, willing and able to exert its economic “discipline” over an aggressive United States, as there had been for Britain in 1956.

In today’s world, any unjustified U.S. aggression against a country as significant as Iran would almost certainly push the other significant powers in the world system — starting with the other five parties to the JCPOA — to work together to discover economic and other “soft power” steps they could jointly take to rein in an errant Washington. The five non-U.S. parties to JCPOA have tried, but so far failed, to build a global payments system that could circumvent the U.S.-dominated SWIFT system and thus allow them to buck the secondary sanctions that Trump has threatened against them. But initial building blocks for two different alternatives to SWIFT have been put in place — one by the Europeans, the other by the Chinese and Russians — and an unjustified U.S. aggression against Iran could see that effort intensified.

It seems that the non-U.S. big powers would today lack the same kinds of powerful, effective tools — whether in the United Nations or the world financial system — that enabled Eisenhower to bring the wayward aggressors of 1956 so speedily to heel. But even if the “other big powers” cannot impose constraints on Washington as swiftly and effectively in 2019 as Washington was able to impose on London, Paris, and Tel Aviv in 1956, that does not mean there will be no constraints on Washington, should Trump and his entourage proceed with an attack on Iran.

The first and most significant of these constraints will be that imposed by the Iranians themselves. Iran is not Gaza, and it is not Yemen. It is not a “target” that can be pummeled and devastated at the will of an assailant, with little power to retaliate. Iran is, as U.S. military planners well understand, a country with considerable strategic depth and resilience, defended by a smart military. It enjoys robust, often battle-proven alliances with capable fighting-forces in Iraq, Syria, Lebanon, and Yemen. It has significant political and economic relationships with numerous pillars of the global economy, including Japan, China, and India. And it is located in an extremely “combustible” (lit. and fig.) region of the world.

If the warmongers around Trump succeed in pushing him into a war against Iran, the “resistance” against the United States and its military will not come only from Iranians, and it will not take only military form. The “other big powers” in today’s world may well not all opt to act together to constrain and roll back a post-aggression Washington. But a significant portion of them will. And given that the the past 29 months have seen Washington summarily pull out of numerous, much-valued international agreements (including, but extending far beyond, the JCPOA), diplomatic thinkers and planners in many different capitals have already started to figure how to build international systems and structures that cannot be wrecked or held hostage by the caprices of a leader in Washington.

We live in uncertain times, but of a few things we can be sure. Any significant, unjustified U.S. attack against Iran will have longterm effects on the balance of power both within the Middle East and far beyond. The war triggered that any such invasion triggers will be very destructive, most likely to the United States as well as Iran and other Middle Eastern peoples — and it may also be lengthy. It will usher in a diminution of Washington’s power in the international system at least as serious as that triggered by President George W. Bush’s unjustified invasion of Iraq. (It will “Make America Smaller, Again.”) And it may well stress the whole system of international institutions and norms that we have known since 1945 close to — or even beyond — breaking point.