What is the Labour party for in a time of war? The left has struggled with that question for decades, but the conflict between Israel and Hamas renders it painfully acute. If Labour isn’t for a ceasefire, an end to the bloodshed, then what is it for? Is it in favour of premature babies dying because hospitals can’t keep their incubators running, of refugee camps being bombed, of once-teeming neighbourhoods being reduced to wastelands? Put like that, the answer may seem obvious, and in emails to many of the 56 Labour MPs who rebelled against the whip on Wednesday night to call for a ceasefire, it will have been put in much more emotive terms. The former shadow minister Rosena Allin-Khan, who rebelled, said that while 99% of the thousands who contacted her did so respectfully, she had had to involve police over “one where someone threatened to come and find me if I didn’t vote their way”. Death threats are sadly not a new experience for Allin-Khan, or many other MPs who have suffered attempted intimidation over a shockingly wide range of issues. But her story is a reminder of just how high feelings are running and of the pressures some MPs are under, whichever way they ultimately voted. Be under no illusions: nobody in Tel Aviv or Gaza City was ever hanging on the results of this vote. Neither Israel nor Hamas are likely to heed some foreign opposition party calling for a ceasefire, yet that is also true of calls for Hamas to release the hostages, and Keir Starmer nonetheless rightly does that at every opportunity. He understands their families’ desperate need to know they haven’t been forgotten, and how deeply their plight is felt in the Jewish community. So why, some Labour supporters will wonder, isn’t the same true of families bombed to smithereens in Gaza? This vote mattered not because anyone was naive enough to think it may change the course of a war, but as a statement of values. But the other reason it mattered is Starmer’s resolve to treat every policy crisis as a dress rehearsal for government, or perhaps more accurately as a stress test. He wants to be seen to grapple with complex realities without resorting to cheap slogans or easy answers, but also to learn from the experience. He is right that those who don’t get into the habit now will struggle with the tough decisions awaiting them in government. And while he could have made this a free vote, allowing MPs to follow their consciences to vote for a ceasefire, evidently that was not the message he wanted to send. The net result has been a wounding blow to his authority. Though the good ones should find a way back when the dust has settled, some of the eight shadow ministers who resigned will be badly missed – arguably none more so than the shadow minister for domestic violence and safeguarding, Jess Phillips. But to claim that this means Starmer’s writ no longer runs in Labour now is wild. Scan the list of those who held the line – some with far slimmer majorities than the rebels, or representing parts of cities with big Muslim communities or hefty support for anti-war Greens – and in some ways it’s surprising the revolt was not bigger. Those who held their nerve will, however, need a more emotionally compelling argument if they’re to defend that position over coming weeks. And for Starmer, that was always going to be the hard part. The added twist is that, for once, it’s the old Labour left and not him who looks closest to the British public, the majority of whom now also support a ceasefire. While pointing triumphantly to the polling numbers has helped him contain unhappiness over the party’s stance on Brexit or immigration, that well worn strategy is no use here. Emmanuel Macron’s decision to break ranks and call for a ceasefire last week has also ramped up the pressure on Labour; the prospect of having to choose between doves in Paris and hawks in Washington over a war in the Middle East will evoke painful memories for anyone old enough to remember France’s decision not to join the invasion of Iraq. All that said, it remains true that calling for an immediate ceasefire is not a neutral act, nor in some circumstances even a compassionate one. Everybody wants the killing to stop in Ukraine too, but so long as the Ukrainians have any chance of gaining the upper hand, calling for a truce would be interpreted as heaping pressure on Kyiv to cut a painful deal with Moscow. Even in wars that have reached a natural stalemate, ceasefires cannot be imposed, merely negotiated, which requires getting both sides to the table. Had Labour been in power when this war broke out, the right course of action probably would have been to accept that “ceasefire now” is more a slogan than a strategy – given Hamas’s implacable opposition to compromise and Israel’s burning desire to defend itself – but work round the clock to create the conditions in which one becomes possible. To sum up this process in a soundbite would always have been hard, but in the early days of the crisis, calling for “humanitarian pauses” may just have covered it. To people now haunted by ever more horrific images every time they open their phones, however, it has come to sound obscenely tokenistic. What’s the point of a brief lull to let a handful of aid parcels through, if within hours the recipients will be bombed again? In the past few days, shadow ministers had started trying to argue that these pauses could become longer ones lasting weeks not hours, and crucially that the whole point of them was to build trust. If a brief cessation were respected by both sides, the next one could be longer, allowing time to talk. These nuances have been hopelessly lost, however, in the rising tide of emotion. What has been missing, too, is an understanding that especially for younger Labour supporters, failing to call something out is considered complicity with it and small symbolic gestures of solidarity mean a lot. If he wasn’t urging a ceasefire or joining a peace march, then Starmer needed more imaginative ways of communicating concern and empathy with those horrified by what is happening in Gaza. The point of stress tests is to identify weaknesses before it’s too late, and this shadow cabinet fortunately still has time for fine tuning. But if there is one lesson to be learned from a rocky week, it’s that standing against the easy answer requires being able to stand for something equally compelling. Gaby Hinsliff is a Guardian columnist