On 12 September 2015 Jeremy Corbyn won Labour leader by a landslide and then went straight to speak to the big refugee rights demonstration in London. This article is from Solidarity 375, just before the voting ended.

Don't mourn, organise", the American trade union activist Joe Hill famously told his comrades in 1915 as he was railroaded to a firing squad on trumped-up murder charges.

If Jeremy Corbyn wins Labour leader on 12 September, we should flip that motto into "don't celebrate, organise!" And if he has a near miss, Joe Hill's original will do.

All the opinion polls since early August show Jeremy Corbyn ahead. They also show him more popular with voters in general than the other candidates.

Corbyn, an unassuming campaigner and supporter of workers' struggles for forty years, has become the seed around which a surge of anti-capitalism, generated by the crashing and grinding of the system since 2008 but previously dispersed and almost "underground", has crystallised.

It will be wrong, terribly wrong, disastrous, if we think that once we've elected Jeremy Corbyn as Labour leader, then we can sit back and let ourselves be towed by the new leadership to a better future.

The basic ideas of democracy, workers' rights, and social provision which Corbyn represents are not such as can prevail just by having a good advocate in the high ground of politics.

They can prevail only by determined and militant mobilisation of the rank and file.

A relatively "moderate" Labour right-winger, Luke Akehurst, has denounced Corbyn's supporters as "moving through the party like ISIS in their jeeps in Iraq". Decoded: he wants to demonise the Corbyn camp, and move against it as the US has moved against Isis. The New Statesman reports that Corbyn "faces a significant number of Labour MPs not merely against him but actively out to get him".

Behind those MPs stand hundreds of "advisers", "researchers", spin-doctors, think-tank people and other careerists. And behind them, the billionaire media and the whole entrenched power of the ruling class. The smear and scare campaigns of the last couple of months — "Corbyn will make Labour unelectable" — are only the start.

They are the minority. A small minority. But compact and rich minorities win unless the working-class majority makes itself organised and compact, striking with a fist rather than flailing with limbs askew.

Corbyn's advisers will tell him to go softly-softly, to woo the maximum number of right-wingers who may grudgingly cooperate for a while.

We've seen where that approach leads with Syriza's decision to form a coalition with the right-wing Anel, to elect a moderate right-winger president of Greece, and to invest in cajoling Hollande and Renzi and Lagarde to sway Schäuble towards less harsh EU policy.

Working-class, socialist majorities need to be made and sustained in dynamic action. Unless the Corbyn campaign presses on to transform the labour movement radically, it will be neutralised and then reversed by the entrenched power of the right wing. If Corbyn wins, we should press him to start by opening out the Labour Party conference at the end of September, allowing debate on rule-change reforms and political challenges usually stifled.

Already in some areas, like Sheffield, Corbyn supporters are organised into active, regularly-meeting, local groups. Elsewhere there have been only rallies and phone-banks without organising meetings. The first step should be to get local groups going everywhere - democratic, active, open to debate, geared both to campaigning on the streets and to transforming their local Labour Parties.

Transforming the unions, too. The great lesson of the last big ferment in the Labour Party, in the early 1980s, is that the left-talking union leaders who had let it happen, by supporting democratic reforms within Labour, also cut it short. Because no similar democratic reforms were made within the unions, the top union officials could meet with Labour's leaders in January 1982, at Bishops Stortford, plan to start reeling back the left-wing surge, and carry through the plan.

The TUC congress assembles the day after the Labour leader election result is announced. Trade unionists should argue for it to raise the pressure on Labour.

Young supporters of Corbyn have a national conference for ongoing organisation on 20 September. We need a similar general conference as soon as possible.

The welling-up of revolt symbolised by Corbyn's success is also manifested in a schedule of demonstrations over the coming months unusually packed even for this busy time of the political year.

On 14 September, 4 October, and 2 November are protests against cuts and for the right to strike. The Right To Strike campaign is organising a contingent on the big TUC demonstration of 4 October in Manchester.

On 12 September and 17 October are protests for refugee rights.

On 18 September and 4 November are student protests against tuition fees and for free education.

We need to have these protests not only big, but voicing clear, radical demands. Socialists must be there, organised, vocal, visible, with our demands to tax the rich and expropriate the banks.

The hard-core socialists, too, must discuss among ourselves, sharpen our ideas, step up our organisation, encourage loose sympathisers to become regular activists. The Workers' Liberty annual conference is on 21-22 November.

An activist's diary

Saturday 12 September, noon: Refugees welcome here! National demonstration. Assemble Marble Arch. March to Downing Street.

Sunday 13 to Wednesday 16 September: TUC Conference, Brighton

Monday 14 September, Protest against trade union bill second reading. 11am: Stunt with details to be confirmed, 6 pm: Rally. Outside Parliament, London SW1A 0AA

Friday 18 September, noon: Grants not debt. Students protest and lobby MPs. Meet at Charing X station, The Strand, London.

Sunday 20 September, noon: Youth and students for Corbyn conference. University College London, Cruciform Building, Gower St, London WC1E 6BT. Called by Labour Campaign for Free Education, Scottish Labour Young Socialists, LRC Youth and others.

Sunday 27 to Wednesday 20 September: Labour Party Conference, Brighton

Sunday 4 October, noon: No to Austerity, Yes to Workers' Rights. TUC demonstration at the Tory party conference. Assemble on Oxford Road, Manchester, from All Saints Park southwards. Right To Strike contingent: assemble outside Royal Northern College of Music, intersection of Oxford Road and Booth St.

Saturday 17 October, 1 pm Dover, 2 pm Calais: simultaneous demonstrations. Open Dover! Open Europe!

Monday 2 November, 1 pm. TUC rally and lobby against new anti-union law. Central Hall, Westminster, Storey's Gate, London SW1H 9NH

Wednesday 4 November, 1pm: National demonstration for free education, London.

Saturday 21 to Sunday 22 November: Workers' Liberty conference, London