The brutality of Iran’s crackdown on protesters is almost unfathomable. Despite the authorities cutting off communications and destroying evidence, it is clear that a regime never reluctant to shed its citizens’ blood has done so with unprecedented zeal, sensing an unprecedented threat from unrest across the country, challenging not only its policies but its very existence.

Officials have reported 3,000 deaths, but human rights groups have tallied many more, and a network of medical professionals has estimated that 30,000 could have been killed. Security forces shot people dead as they fled a fire and are arresting doctors for helping the wounded.

Alongside the fury at this vengeful regime is anger at another leader: Donald Trump, who urged Iranians to keep protesting and promised them that “help is on its way” – then played down the slaughter. Now the US president has warned via social media that “a massive Armada is heading to Iran”, and that “the next attack will be far worse” than Operation Midnight Hammer, the US strike on nuclear sites last summer. Iran’s muted response, and its weakening over the last year, has emboldened him, as has his seizure of Venezuela’s Nicolás Maduro, referenced in his post. But protesters were forgotten: instead his demand was “NO NUCLEAR WEAPONS”.

Mr Trump is notoriously unpredictable: in his first term, he called off an attack on Iran 10 minutes before it happened. But his newfound interventionism has wrenched the spotlight from the Epstein files, and Iran threats distract from Immigration and Customs Enforcement brutality at home and his climbdown over Greenland. Iran is a far more popular target than Denmark among his base.

Many Iran analysts now see a “zombie state” – unable to ensure even a basic standard of living or to defend its sovereignty; apparently unable to renew itself; but as tyrannical as it is frail. However, military intervention could come at huge human cost and would not bring democracy – even if that were Mr Trump’s aim. More likely would be the emergence of a strongman, perhaps from the Revolutionary Guard, or regime collapse and chaos. If he were serious about non-proliferation, the best hope – albeit now harder than ever – would be to seek a revised version of the JCPOA deal which he did the most to destroy.

Israel sees a weakened, chaotic Iran as in its interests. Turkey, Saudi Arabia and others are trying to hold the US back because they fear a strengthened Israel, a surge in migration and instability in a region attempting to sell itself as a dependable investment. As weakened as it is, a cornered regime could still do damage – particularly in the strait of Hormuz, a critical artery for global trade – if it believes that inaction would only make it look an easier target. Economic concerns seem more likely to shift Mr Trump than humanitarian considerations.

The EU on Thursday designated the Revolutionary Guard as a terrorist entity – a largely symbolic measure given the extent of existing sanctions. Governments can and should press for a moratorium on executions, support attempts to reconnect Iranians with the internet, and fund NGOs documenting abuses. In the longer term they should consider how to support civil society and help to strengthen it. They should also provide safe passage to activists whose lives are in danger. Military intervention is not the answer – but neither is indifference to the suffering of Iranian civilians.