THE Holocaust remains the goriest testimony to the depravities that racism can incite. Its true extent may be gauged by the legal framework that was created to make it possible. Textual comparison of the Nazis’ Nuremburg laws — stripping Germans of the Jewish faith of their civil rights, excluding them from certain professions, confining them to parts of their cities, towns and countryside and denying them the protection of the law — with the statute books of many colonies in Africa and Asia reveals alarming parallels.

Laws enforced in their colonies by the UK, France, Belgium and other colonial powers before and after the First World War made the exercise of arbitrary power by even junior government officials normal.

In her study of totalitarianism, Hannah Arendt reminded us that the methods the Nazis used in their occupation of Europe were rehearsed in their colonies by all the powers involved in the Second World War. The dehumanisation of those defined as "the other" had been given the dignity of law, sustained by a misanthropic ideology of racial superiority. The objectification of colonial people, which made atrocities morally acceptable, was extended to "untermenschen" — Jews, Romanies, Slavs — or anyone else the Nazis targeted.

These terrifying continuities between empire building and the Holocaust came to mind as we marked International Holocaust Remembrance Day on Sunday. In 1864, the European powers adhered to a number of conventions to regulate the conduct of war. To make war less inhumane, what became known as the Geneva Conventions were further elaborated in 1906 and 1914. The cruel irony was that European efforts to reduce and contain the brutalities of war coincided with an era of the most aggressive European expansionism. Colonial wars pitted the industrial might of Europe, the US or Japan against preindustrial societies. That alone radically escalated the kill rate in battles.

At Omdurman in the Sudan, about 10,000 Mahdists were killed, 13,000 wounded and 5,000 taken prisoner. British general Herbert Kitchener lost 47 men, with 382 wounded.

While they sought to reduce the horrors of war as they built and defended their empires abroad, by their own actions in their colonies, these powers undermined that objective. On display in museums, in hundreds of western public institutions and even in private homes, one finds the rich spoils of wars of conquest waged in the colonies and in Europe. Thousands of objets d’art from every part of the world testify that it was accepted practice to loot territories seized in war.

From September 1939, when the Nazis invaded Poland, they conducted themselves like conquerors in the colonies, violating the Geneva Conventions. In the Far East, their ally, Imperial Japan, set its own record of war crimes in occupied countries and in prisoner of war camps.

The axis powers seized both state and private property in countries they overran. The populations of occupied countries were reduced to subjects. The Nazis deported and relocated entire communities; stripped them of their property; and they did not hesitate in dealing out the harshest retribution, including collective punishment, when they encountered resistance.

The violence that had been exported to their colonies came home to roost when the Nazis began applying these methods in Europe. Genocide in Europe recapitulates the fates visited on many indigenous peoples. It is its sheer scale and the application of modern technologies that makes the Holocaust so terrifying.

After the Second World War, the Geneva Conventions were reviewed and further elaborated in 1949. Two additional protocols, applicable to unconventional wars, were adopted in 1977. Yet international humanitarian law was systematically violated, especially in the colonial wars in Indo-China, Malaya, Kenya and Algeria. The fifth amendment to the US constitution was conceived as a disincentive against torture by protecting suspects against self-incrimination. In the 21st century, interrogation methods associated with the Spanish Inquisition are actively advocated by prominent politicians.

The Pandora’s box of impunity was opened even wider in the 21st century. In flagrant violation of the 1977 protocols, prisoners of war taken in an unconventional war in Afghanistan have been detained for more than a decade. The former vice-president of the US openly admits to their torture. Prisoners taken in an interstate conflict in Iraq were systematically humiliated, degraded and tortured by their captors. Can any US soldier claim the protection of the Geneva Conventions in the knowledge that US forces humiliate, degrade, waterboard and torture the combatants of opposing armies?

The lessons of appeasement also appear to be lost as we watch Israel grab "lebensraum" as fanatical Zionist settlers occupy Palestinian land and resistance to such encroachments is suppressed by the Israeli Defence Forces.

Are we witnessing a return to barbarism because the international community has set the bar of acceptable conduct by states so low? Our humanity demands we do better.

• Jordan is former arts and culture minister.