There is an old Iranian proverb: “You don’t put the wooden pot on the fire twice.” Someone needs to tell that to Donald Trump, who risks plunging the US into its fifth disastrous conflict in two decades – after Afghanistan, Iraq, Libya and Syria – with no more clue than his predecessors about the consequences, the cost, the aftermath or the exit strategy.

I shed no tears over the death of General Qassem Suleimani, a man of violence whose legacy is written in the blood of innocent civilians. But make no mistake, the Trump administration’s decision to assassinate him, and breach Iraq’s sovereignty to do so, was a wilful attempt to push Iran to the edge of a war that would put millions more lives at risk.

As with everything else Trump has done with regard to Iran since coming to office, starting with his sabotage of Barack Obama’s nuclear deal, his latest act has simply served to strengthen the grip of the hardline theocratic and military wing of the Iranian regime, who have bitterly resented attempts made in recent years to build better relationships with the west.

Whether this strategy has been deliberate or simply perverse does not matter. The hardliners are now firmly back in control, and their only reaction to Suleimani’s assassination will be to escalate the tension they crave still further, and retaliate on a greater scale. This is no longer tit for tat; it is classic brinkmanship, and when neither side can afford to lose face with their domestic audience or international counterparts, we can only fear the outcome.

Let’s remind ourselves that Iran is almost four times the size of Iraq, five times the size of Vietnam and nine times the size of Syria, with a population of 83 million and the 10th-biggest army in the world.

Do we have the courage that Harold Wilson showed during the Vietnam War, and refuse to join in?

And while the armchair generals think that another round of “shock and awe” will overcome that, they still have absolutely no plan for what will follow, or for how a postwar Iran would function – just as they had no plan for Afghanistan, Iraq, Libya or Syria.

So we face a central question here in Britain. Do we repeat the experience of those other conflicts, and get dragged into this quagmire by Trump, or do we have the courage that Harold Wilson showed during the Vietnam war, and refuse to join whatever coalition he cobbles together if the conflict continues to escalate?

I have seen some politicians describe this as a choice about whose side Labour is on: the US or Iran. To which my answer is, I’m on Britain’s side. And I would never put our brave British servicemen and women in harm’s way to fight a war that would risk unimaginable suffering for the civilian population of Iran, and unforgivable losses for our own forces.

Patriotism is not jingoism. And, for me, being patriotic means thinking about the families left behind – and all too often left bereaved – when their loved ones are sent away to fight wars we should have no part of, and that have nothing to do with the defence of our country, but everything to do with the crazed belligerence of foreign leaders.

Having shadowed Boris Johnson for the two years he was foreign secretary, I have no confidence that he will make the right decision on this issue. It is astonishing to me that, in more than 48 hours since the assassination, he has not made any statement about a crisis that is on the brink of becoming an even more destructive and catastrophic war than Iraq or Syria.

Is he afraid of angering Trump? Or is it simply that, as he lounges in the Caribbean sun, he simply does not care, an exact duplicate of the blase approach to Iran that he took in 2018 – when he was foreign secretary and Trump was driving the nuclear deal to destruction – and the previous year when he recklessly jeopardised the fate of Nazanin Zaghari-Ratcliffe?

Whoever becomes Labour’s new leader, they need to have the strength, experience and knowledge to lead parliament in fighting back against Britain becoming embroiled in this disastrous drift to war.

Otherwise, the wooden pot will soon burn again.

Emily Thornberry is the shadow foreign secretary