Israel has all but declared war in the Middle East – a conflict it cannot hope to win | Simon Tisdall

Failure to halt the war in Gaza lies at the heart of the latest lethal savagery in the Middle East. The assassination in Tehran of Hamas’s political leader, Ismail Haniyeh, will be celebrated in Israel as just revenge for the 7 October atrocities. But Islamist hardliners in Iran and militant groups across the Arab world will see it as further proof of their belief that the state of Israel is a menace that must be destroyed at all costs.

And so the hatred, the violence and the misery will continue unchecked, and will in all probability worsen and spread. Just because this homicidal cycle is familiar does not mean it cannot accelerate. Few parts of the Middle East – Lebanon, Syria, Iraq, Yemen, Egypt, Jordan – have escaped the toxic fallout of the Gaza conflict. In Washington DC and Britain, domestic politics are roiled by the fury and the grief. The UN’s impotence is daily, humiliatingly exposed. No one is immune to this poison.

It would have been preferable if Haniyeh, in common with Hamas leaders based in Gaza, had faced trial at the international criminal court (ICC) – and been made to answer for his crimes. That now cannot happen. Instead, Israel has once again sought “justice” through extrajudicial murder. Only in April, a covert Israeli strike on Iran’s consulate in Damascus killed a top Iran Revolutionary Guards Corps general – and brought the region to the brink of all-out war. There have been numerous similar killings.

The man overseeing these assassinations, Benjamin Netanyahu, Israel’s prime minister and chief architect of the continuing genocidal campaign against Palestinian civilians in Gaza, should be forced to answer for his crimes, too. The ICC’s chief prosecutor is trying to ensure that happens , despite US opposition. But there is little sign it will. More likely, given the example he sets, is that Netanyahu will himself be targeted by assassins.

Tuesday’s almost simultaneous, reported killing of a senior Hezbollah commander, Fuad Shukur, in an Israeli airstrike in south Beirut, will help ensure the Middle East’s downward spiral into destruction continues to accelerate. Once again, the Israel-Hamas war is the driving factor. The attack was in retaliation for an alleged Hezbollah missile strike in the occupied Golan Heights last weekend that killed 12 young people .

Yet the main reason Hezbollah is firing missiles into Israeli-held territory now is Gaza. The organisation’s leader, Hassan Nasrallah, has been relatively restrained since 7 October, given the huge military resources at his disposal. Nasrallah says cross-border attacks will stop when there is a ceasefire in Gaza. Killing Haniyeh, a senior Hamas decision-maker and negotiator, makes such a ceasefire even less likely, at least in the short term. Killing Shukur is another dangerous provocation.

It is also worth pointing out, amid the frequently overwhelming welter of daily horrors, that two children were killed and 74 people injured in the Beirut airstrike, according to Lebanese officials. But then again, Israeli forces have been killing Gaza’s children with impunity for months. The UN puts the total at 15,000 dead. Two more deaths barely register (except with parents and families ).

It’s not that Israel is blind to the broader consequences of its role in this endless, vicious cycle. But it says that everyone else is to blame. “Hezbollah’s ongoing aggression and brutal attacks are dragging the people of Lebanon and the entire Middle East into a wider escalation,” a military spokesperson said . “While we prefer to resolve hostilities without a wider war, the IDF [Israel Defense Forces] is fully prepared for any scenario.”

The wider war Israel “prefers” to avoid is, in fact, already raging. Israel repeatedly bombed Yemen’s Red Sea port of Hodeidah this month after a drone attack on Tel Aviv by Tehran-backed Houthi Shia militants. Netanyahu, whose answer to almost every problem is extreme violence, boasted the bombing “makes it clear to our enemies that there is no place that the long arm of the state of Israel will not reach”. That sounded very much like a declaration of war on the entire region. Yet it’s a war Israel cannot ultimately win.

Related: A new terror has entered the Gaza war: that it is ushering in an age of total immorality | Nesrine Malik

Once again, the Houthis say the principal reason they are attacking Israel, and shipping in the Red Sea – attacks that have sucked the US and Britain into risky military action – is Gaza. If there’s a ceasefire, they claim, their attacks will halt. This is hardly radical. This is the same Gaza notional ceasefire backed , in theory, by the US, Britain, the EU and the UN security council. This is the same ceasefire millions of people in the Arab world, Europe and the US have been demanding for months. This is the same ceasefire that still – still – doesn’t happen.

Will a humiliated Iran hit back directly over the Haniyeh killing? Will Hezbollah escalate? Will a divided Israel, its reputation further disfigured by the torture and alleged sexual abuse of Palestinian detainees , plunge deeper towards national disintegration as far-right zealots, backed by Netanyahu’s ministers, storm army bases to free the alleged abusers? Quite possibly. No outcome is off the table in a region where the so-called rules of the game that hitherto prevented an all-consuming conflagration are being burned page by bloody page.

People say the Middle East is complicated. It is. They say there are no answers. This may be true. But despite the rockets, Gaza is not rocket science. It’s not that complicated. Stop the war. Stop the killing. Save the children. Agree a ceasefire and free the hostages. And then all the other problems, while not going away, may become just a little easier to manage.

• Simon Tisdall is the Observer’s foreign affairs commentator