A general who fights the previous war usually loses. When French commanders built the Maginot Line in the 1930s it was with the first world war in their minds. They proved that leaders who think they can win by imagining today’s battles can be fought on yesterday’s terrain will find themselves outflanked. But what can one say of a leader who thinks that victory can be secured by repeating a strategy from the last war that brought defeat? That is what Jeremy Corbyn is in danger of doing.

Labour’s leader is coming under fire for sticking to his guns on antisemitism and Europe. Mr Corbyn’s refusal to shift position might be explained because both issues were dogs that barked in the last election but did not bite. Labour lost in 2017 but defied pundits who claimed Corbynite policies would destroy the party. Although he beat expectations, Mr Corbyn’s message did not carry him to Downing Street. Labour’s anti-austerity pitch struck a chord with voters tired of Tory penny-pinching but the issues of anti-Jewish discrimination and Brexit did not go away. They only became more acute.

Mr Corbyn has perhaps taken the wrong lesson from the 2017 result – not that the context has changed but that he can re-enact history. The result has been both tragedy and farce. He has made mistakes with dealing with serious allegations of antisemitism within Labour’s ranks. He was in charge of an underwhelming response to a growing crisis. Mr Corbyn was wrong not to meet last year Jewish critics within his party worried about the torrent of abuse they faced. Somewhere along the way the Equality and Human Rights Commission launched an inquiry into how Labour has handled antisemitism. It is hard to explain how such events could occur. Perhaps it was that people who consider themselves honest anti-racists acting in good faith thought that they can never be responsible for deplorable acts. The Labour leader has been a principled defender of the Palestinian people. But Mr Corbyn needs to root out antisemitism within his party and stand up for Palestinian rights.

A BBC Panorama investigation has sent shockwaves around Labour before it has been broadcast. The lawyer hired by the party in 2018 to help tackle the mess over anti-Jewish abuse has left his post, it emerged this weekend. The party needs a new procedure with clear rules and penalties to deal with claims of antisemitism. Last year saw a record number of antisemitic incidents recorded in the UK. There needs to be a recognition that accusations of Jew-phobia are not just the deliberately insincere work of Blairites who are seeking a way to bring down Mr Corbyn or to prop up the Israeli state. Labour will have to find a way of having a conversation with many Jewish people who have lost faith in it. Mr Corbyn could begin to win back trust by taking charge personally of the fightback against racism in the party.

On Europe, Labour’s ambiguous positioning worked to some degree while a viable soft Brexit option was on offer. With the arrival of Boris Johnson as prime minister, the compromise solution assuredly vanishes. There is no single magic answer to the underlying causes of Brexit. The past is no solution. That is partly why the Guardian has been – and continues to be – cautious about advocating a second referendum on Brexit as the solution to this wider failure of politics-as-usual. We have consistently argued for a national deliberative debate, a citizen’s assembly, to buttress the parliamentary process. Yet Labour has not moved on from its 2017 manifesto.

The Brexit choice that lies ahead looks likely to be between Mr Johnson’s disastrous no-deal and a second referendum vote. If that is the case then Labour ought to back a reformed Britain within a reformed EU. Mr Corbyn should not abandon the promise of his leadership. He was right to call for a more elevated tone in politics, repudiating cheap partisanship. Yet on two big issues at Labour’s core he has failed to don the statesman’s mantle for which he grasped. That is a concern. Mr Corbyn might take solace from the knowledge that for most voters the ins and outs of such debates are meaningless. But he must be aware that the bare bones of the story will tell them all they need to know. The task for Mr Corbyn is to shift the narrative with deeds as well as words.

• This article was amended on 9 July 2019 to clarify that the lawyer hired by Labour, Gordon Nardell QC, left his post prior to news reports of his departure this weekend. Text was also added to clarify the timing of a proposed meeting between Mr Corbyn and Jewish critics.