Seventy years ago today — April 15, 1945 — British troops entered the fairy tale town of Celle in Lower Saxony and abruptly found themselves on the threshold of hell.

Outside Celle the British units, which included a number of Bermudians who had volunteered for overseas service in the Second World War, were confronted by unprecedented scenes of man’s inhumanity to man, writ large and in the blood of innocents.

Just a few miles beyond the town’s half-timbered houses, cobblestone streets and centuries-old chestnut trees, Germany’s Nazi dictatorship had built the Bergen-Belsen concentration camp complex.

The troops who liberated Bergen-Belsen found themselves face to face with mountainous jackstraw heaps of emaciated corpses, diseased survivors who envied the dead and the ruins of a diabolical philosophy predicated on the perverse notion that mass human sacrifice could renew and purify Germany.

Nazism may have been an entirely secular 20th century political dogma but the impulses which animated it were as old as the oldest religious rituals involving blood offerings to the gods.

Bergen-Belsen and its five satellite camps instantly became synonymous with and emblematic of the Nazi policy of exterminating Untermensch — those deemed to be “undermen” or subhumans by the state.

There were no gas chambers at Bergen-Belsen or any of the other ghastly apparatus of mechanised slaughter which the Nazis installed at other camps. The inmates at Bergen-Belsen were literally worked to death as slave labourers or died of disease — typhus was rampant — or simply succumbed to the active neglect of their captors.

Tens of thousands of Jews, Czechs, Poles, anti-Nazi Christian activists and Roma died there in the two years Bergen-Belsen was in operation as a concentration camp. Among the casualties was Anne Frank, the young Dutch Jewish diarist.

Her first-hand account of life in hiding from the Nazis was later published and remains a timeless gift to the world, one which demonstrates that hope, humour and compassion are still capable of illuminating the human condition even during history’s darkest hours. She is thought to have died just a few weeks before the British 11th Armoured Division entered Bergen-Belsen.

History is, of course, replete with unspeakable tragedies and crimes against humanity. But the organised and systematic killing of entire groups — supposedly to heal a wounded country or people — is a relatively modern phenomenon. The emergence of what we now call genocide broadly coincided with nationalism replacing religion as the answer to people’s spiritual needs in the 19th and 20th centuries.

Turkey’s annihilation of its Armenian population in the years immediately following the First World War prefigured the Nazi “Final Solution” in terms of fanatical zeal if not actual ruthless, centralised German efficiency (the word genocide — the murder of a people — was actually coined in 1943 to describe the mass extermination of Armenians).

In recent years the world has witnessed the fratricidal carnage which has erupted in countries as diverse as Cambodia, Bosnia and Rwanda when ultra-nationalist, quasi-millenarian regimes have resorted to wholesale slaughter of victimised groups to further their political, cultural and social ends. The Turkish and Nazi genocides were clearly not anomalies. If modern history demonstrates anything, it is that ordinary people everywhere in the world are capable of becoming socialised and acclimatised to the intolerance which leads to death warrants being signed against designated Untermensch.

However loudly and however often we have chanted “Never Again!” since 1945, racial, ethnic and cultural differences have repeatedly been used as intrusive wedges by ideological zealots to drive peoples apart in the post-Second World War era.

In all instances, an unyielding belief in one absolute truth has led to a dogmatic intolerance of others’ points of view — and, ultimately, a surpassing contempt for others’ lives.

One of the Bermudians who took part in the liberation of Bergen-Belsen reflected on his life-changing experiences at the camp complex in a letter he wrote late in life to his son.

An eyewitness to the seemingly boundless limits of human cruelty, mass violence and state-sanctioned bigotry, he said: “I discovered when I was at the camps that Evil is not simply a religious conceit; it is a real and palpable force in this world.

“But I also learned that Kindness, Decency and Tolerance are equally real — and act as powerful countervailing forces to Evil. I’m sorry if this sounds a bit like Dale Carnegie, one of those ‘If life hands you a lemon ...’ banalities.

“But if I didn’t believe this to be so, I doubt I could believe in anything ever again.”

In a world where ISIS is beheading or incinerating those it deems apostates and Boko Haram and the Taliban are executing schoolchildren for having the temerity to want an education, we could all do worse than to believe the same thing.