Last week I took part in the Holocaust Educational Trust’s Lessons from Auschwitz one-day visit to Poland.

It is impossible to comprehend the scale of what happened during the Holocaust without seeing where it took place. In a fittingly cold and dark Auschwitz, seeing is truly believing. The display of tens of thousands of victims’ shoes sends a chill but it feels impersonal and anonymous. Indeed, one of the most powerful experiences in my Holocaust education has been the first-hand testimonials I have heard from survivors. What then for my young children who will come of age when there are no survivors left to tell their story?

The work of the Holocaust Educational Trust is second to none. By occasionally pausing in the vast open space of the Birkenau camp to read a survivor’s testimonial, the educators keep alive the memory of those who perished by reminding us of the individual - the mother, the husband, the brother, the baby. Without an account of the man, woman or child who was tortured, starved, dehumanised, and murdered, all you have is a statistic. The most harrowing realisation is that this isn’t ancient history, it happened in the lifetime of people living today. It is a mere accident of birth that we live today and not then.

By coincidence, the visit took place on the November 7, the 100th anniversary of the Russian revolution. While reading about the centenary at the airport, I found myself overwhelmed by the enormity of history - the multiple accounts of dehumanisation, mass murder, and mercifully, the story of liberation. I felt at that moment an immense gratitude for my freedom and liberty and made a pledge to ensure my children know no different. My freedom commands that I do everything I can to protect what's so precious but, sadly, so vulnerable.

And while this might sound like hyperbole, history shows us not to be complacent, even when something may seem unthinkable. As the author Anne Applebaum wrote in an outstanding essay marking the Russian revolution, “so discredited was bolshevism after the Soviet Union’s demise in 1991 that, for a quarter of a century, it seemed as if bolshevik thinking was gone for good. But suddenly, now, in the year of the revolution’s centenary, it’s back”.

Those who romanticise communism are speaking to a generation that don’t remember the past. As Applebaum so evocatively cautions when she talks about "neo-Bolshevism", we cannot rule out fringe figures, for on the eve of the revolution, most of the men who led it were the fantasists on the margins of society.     

I am resentful towards those who either seek to deny the past or who are complicit in trying to refashion it. That there is such a thing as Holocaust denial repels every fibre in my body. On Poland’s national Independence Day last week, thousands of nationalists marched for a “pure Poland, white Poland”, chanting “pray for an Islamic Holocaust”. Poland’s interior minister said: “We are proud that so many Poles have decided to take part in a celebration connected to the Independence Day holiday”. If this can happen when we have living and breathing survivors, traumatised souls, how much further will we descend when that memory fades?

"Never again" means challenging the ideas which lead to genocide. It is too late to fight it when the ideological war has been lost. So while we may think that fascism and bolshevism have been discredited - and in many respects they have been – we must be alert to a creeping resurgence.

I question the authenticity of those who claim to be allies in the fight against antisemitism but don’t do everything they can to fight it from whichever arena it arises, be it from the far right, the far left, or from Islamism.

Those with a nefarious agenda must be denied any and all legitimacy. If you are only half an ally, I contend that you are no ally at all and I am prepared to lose friends by saying so, because the enormity of what we face does not bear thinking about. To borrow from the great survivor, Elie Wiesel: “We must take sides. Neutrality helps the oppressor, never the victim. Silence encourages the tormentor, never the tormented”. 

Claudia Mendoza is director of policy and public affairs of the Jewish Leadership Council