iri, define masochism: how about any attempt at a rational or balanced discussion of Labour’s last five years? Why pick at a still infected old wound when everything is on fire, you might reasonably ask, and when only a predictably toxic mix of score-settling and defensiveness will result? There is nothing to be learned from a morally disgraced political aberration except as a salutary lesson in where self-indulgent radicalism leads: here is the standard narrative embraced not just by the British right but many self-described progressive commentators. For some on the left, the electoral rout of December 2019 was the product of a scorched-earth policy adopted by Jeremy Corbyn’s internal opponents, a remorseless onslaught from a near-uniformly hostile media and nothing else. That leads to a fatalistic conclusion: that any political project promising transformative change is inherently doomed. The reason I have spent the last six months interviewing dozens of Labour figures about the past five years for my book This Land is to provide a nuanced understanding of an often-traumatic half-decade to help chart the party’s future course. Corbynism wasn’t an accidental glitch in the matrix. The battery of cuts that followed the financial crash – and Labour’s failure to offer an inspiring or coherent alternative to it – forged a large, disaffected constituency who felt unrepresented by mainstream politics. It was they who latched on to an implausible candidate for leader. Corbyn’s Labour opponents no longer had a story to tell, no compelling answer to an economic model that no longer generated rising living standards. Labour was on the verge of political bankruptcy: a party founded to represent the working class had come to abstain on a Conservative welfare bill that hacked away support for low-paid workers. While Corbynism attracted unprecedented support from economically insecure and socially progressive younger voters, it crashed among disproportionately socially conservative homeowning older people who – rightly – have had their living standards protected since the global financial system nearly collapsed. These underlying dilemmas remain. There are profound lessons that do need to be learned. One is the sheer toxicity of culture wars to any political project that seeks to redistribute wealth and power. Brexit is an endless generator of culture-war divisions, a drunken bore at the dinner table who forces the other guests into infuriating arguments. Yet there was a fatal complacency from within the Corbyn project from the very beginning: a belief that Brexit was a Tory psychodrama and thus would always cause more damage to their opponents, perhaps splitting them like the Corn Laws did in the 19th century. During the referendum campaign, most people in the leader’s office were not Lexiteers, but they “did not take it seriously at all”, as one former Corbyn aide put it to me. “Most thought, if we left, it wouldn’t really cause us any political difficulties.” That fateful attitude later collided with the triumphalism of the 2017 election, partly explaining why Labour was so slow at defining a Brexit approach: after all, Theresa May was “a dead woman walking”, in the words of George Osborne, and Brexit would devour her and the party she led. This combined with Corbyn’s greatest strength and weakness – his pathological aversion to conflict, which initially defused Tory attack lines that he was a dangerous extremist, but led to a destabilising inability to take decisions – to create a vacuum, later filled by the People’s Vote movement, which convinced remainers they should hold out for a second referendum. They disastrously toxified any option among remainers other than a new referendum. Learning from the catastrophe of 2019 doesn’t mean pretending the 2017 election did not happen. “You lost then, too!” comes the predictable response, airbrushing the consensus after the 2015 defeat – including a near total wipeout in Scotland – in which few believed the party could triumph in a hypothetical 2020 election, let alone within two years. Even MPs who were profoundly opposed to Corbyn were clear at the time that the manifesto pledges were instrumental in Labour’s biggest vote surge since 1945, rather than simply attributing the party’s breakthrough to a shambolic Tory campaign. That election restocked Labour’s otherwise empty intellectual cupboard. In the age of Blairism, even raising the rate of tax on top earners was seen as electoral suicide: but the political debate within today’s Labour revolves around which Corbyn-era policies should be kept or ditched. But if the left wants to salvage those policies for today’s Labour party, it needs to be honest about what went wrong. Corbynism was undoubtedly severely damaged by internal sabotage; but the leadership operation itself was often profoundly dysfunctional and demoralised, something that wasn’t rectified because of post-2017 hubris and Corbyn’s avoidance of conflict. A top team that was united descended into brutal acrimony long before the election was even called. Those who insisted the antisemitism crisis was a smear campaign and nothing else – that Labour’s opponents would always seize on it did not mean it was not a very real problem – not only caused pain to Jewish people but also helped strip away Corbynism’s idealistic sheen. Labour’s recent past remains a battleground largely fought in the hothouse of social media, where bitter conflicts can be reignited and blame attributed. It will only metamorphose into something to be learned from when passions subside: we remain far from that point. Some within Labour want to establish a year zero, which simply consigns the last five years to a dustbin labelled “Never to be repeated”, but while that might suit factional ends, it advances no debate about the party’s future in an era of unprecedented social turmoil. The need for a transformative political agenda is far greater now than when Corbyn first stood: but without a balanced understanding of the last five years it will prove impossible. • Owen Jones will be in conversation with Frankie Boyle at a Guardian Live online event on Wednesday 16 December to discuss his new book, This Land, and the rise and fall of Corbynism