Garvan Walshe is a former National and International Security Policy Adviser to the Conservative Party. He runs TRD Policy.

Missiles fired into Saudi Arabia by Iran-backed Yemeni rebels. Attacks on US installations in the Baghdad Green Zone. Two separate attacks on oil tankers in the Persian Gulf. The last fortnight has seen an escalation in implausibly deniable Iranian activity: acts that in all likelihood have Tehran’s blessing but can’t definitively be attributed to them. What’s going on?

Monday’s announcement from Tehran that it is resuming nuclear enrichment above the threshold allowed by the Joint Comprehensive Plan of Action (JCPOA) is an important sign. This is no ordinary Iranian trolling of the US but a strategic move to exploit the Trump administration’s diplomatic weakness.

A nuclear arsenal would transform Tehran’s status in the region, put it ahead of its Gulf Arab rivals, and allow it to ratchet up its threat against Israel. Gulf states could respond in kind and build (or buy) bombs of their own. Israel would risk a major war and conduct air strikes at the very edge of its capability to stop it.

Yet preventing a determined regime from acquiring nuclear weapons is hard. The technology is 70 years old. The engineering expertise required is not especially advanced, and can be developed under the guise of nuclear power generation. That’s why non-proliferation efforts have focused on controlling the production of fuel, and in particular the process of enriching uranium from the level useful to generate electricity, to that which can be used to make a bomb.

The Non-Proliferation Treaty that commits signatories (which include Iran) only to develop peaceful nuclear capability has a flaw. It’s too easy for a country to leave the NPT, and then make a dash to enrich uranium before the international community can get its act together to stop the offending state: this is called a breakout. And while Argentina and South Africa voluntarily abandoned nuclear programmes as they transitioned to democracy, Pakistan, Iraq, Syria and Israel (not a signatory to the NPT) all managed to escape detection. Iraq’s and Syria’s programmes were only destroyed by Israeli military action.

The JCPOA aimed to extend Iran’s nuclear breakout time from months to years, in exchange for lifting sanctions. It was supported by the five permanent members of the security council and Germany; and, also, the Israeli general staff who are widely thought to have thwarted Netanyahu’s plans for a military strike against Iran’s nuclear operations.

Though the JCPOA was opposed by elements of the US national security establishment, who wanted to renegotiate it, Trump wanted to abolish it altogether. The Trump administration not only withdrew the US from the JCPOA, it also imposed its own sanctions on non-American companies doing business with Iran. It used American economic weight to force them to choose: do business with Iran and we’ll cut you off from the American market.

Though the European powers have set up a France-based financial vehicle to allow trade with Iran without using parts of the international financial system controlled by the US, European businesses know the US market is far bigger than the Iranian one, even for oil industry firms. This was Trump’s strategy: leave the JCPOA and use America’s economic muscle to keep Iran’s economy under boycott, even without formal international sanctions.

This has left Iran with nowhere to turn. With inflation high, and the currency falling, the country has gone back to a siege economy. Good though this may be for the Revolutionary Guards who make money from the smuggling, it also suggests the JCPOA got them nothing because the US didn’t just leave the deal, but managed to enforce its pre-deal policy from outside it. Conversely, because the US is already in effect enforcing global sanctions, it can’t achieve much by seeking to formalise them. If Iran has nothing left to lose by breaking the JCPOA, the US has nothing left to use to stop them.

Nothing that is, except military force.

Unlike Iraq or Syria, Iran’s much more capable state has taken steps to protect its nuclear facilities from attack. It has dispersed them across the country; located them near populated areas and buried them underground. This does not make them impervious to attack, but does mean that a mission to destroy them is likely to involve the prolonged presence of troops on the ground, and a dash across the country as Iran moved its equipment around its rather large territory.

This would have been a difficult, though not impossible, case for a US administration in good standing, supported by its European allies and with Chinese acquiescence, to make. Clear evidence of Iranian nuclear activity could compel them to tolerate a US intervention.

This is not such an administration.

It’s headed by a compulsive liar. The State Department has been gutted. Career officials have left, and Trump has failed to appoint Republican officials to senior ranks. The Republicans’ own national security establishment despairs at the President’s behaviour and would attack him for adventurism. Meanwhile Trump has done almost everything possible to alienate allies with military capability, from Canada and Mexico, to Germany and Australia. The Iraq war would command international consensus by comparison.

Domestic politics are little better. Trump’s ratings are so bad he fired his pollsters. He lacks legal authority to use force on a scale necessary to eliminate Iran’s nuclear progrmme (and adapting the Authorization to Use Military Force from 2001 after 9/11 would stretch legality in a way that even his administration would find difficult to manage). He campaigned on withdrawing troops from harm’s way in the Middle East, not sending them over there. And a war justified to deal with weapons of mass destruction faces a higher burden of proof after Iraq.

Nor is Trump the warmonger he sometimes likes to appear to be. He swaggers and threatens, but is sentimental and averse to bloodshed. He authorised sanctions on Russia after the attempted assasination of Sergei Skripal after seeing pictures of ducks that had died in the attack. Worried that his National Security Adviser is bent on a military confrontation of Iran, he had his staff brief against John Bolton. He’s even taken to calling the likely Iranian attacks on the tankers “very minor.” This is not a man itching to fight.

America’s present is embattled domestically and weak abroad. His administration is understaffed and scorned by competent officials. His allies don’t trust him because he doesn’t feel bound by his own agreements. He speaks loudly but doesn’t carry much of a stick .If there were ever a time for Iran to build a bomb without the world getting its act together to stop them, these next 19 months of Trump would surely be it.