President Donald Trump’s retweeting of anti-Muslim videos propagated by Britain First has made millions more people around the world aware of the European far-right’s crude Islamophobia.

Is this racism a retargeting of familiar tropes of anti-Semitic hatred? Or does anti-Muslim and anti-Jewish hatred have a more complex relationship, both in history and in our current moment?

Prejudice toward Islam and Muslims is endemic in the Europe of 2017. The "Muslim Question" is central to the politics of the far right, which has achieved success unprecedented since WWII at the polls this year, from France to the Czech Republic via Austria and Germany.

Open gallery view Trump retweets far-right British leader's video: 'Muslim migrant beats up Dutch boy on crutches!' Credit: Screenshot / Twitter

More significantly, the fear of Muslims as potential terrorists has become an integral part of mainstream European politics and the European security state, as has been identified by Amnesty International, among others.

Several commentators and academics have argued that this groundswell of Islamophobia, which began in earnest with the "war on terror" after 9/11 and has gathered pace since 2015, has made Muslims the "new Jews" of Europe. They contend that today’s emergency is redolent of the anti-Semitism of the 1930s, or of the late 19th century.

This argument is, however, inherently flawed.

Comparing the two racisms in two completely different periods of history, jumping across time, misses entirely the complex evolution of the relationship between anti-Semitism and Islamophobia that has taken place over more than 1,000 years. This shared story produced profound connections, but also differences, and, by the middle of the 20th century, led to the apparent splintering of these racisms.

We need urgently to pay heed to this dynamic history if we are to grasp the world’s current racism emergency.

Hating Jews and hating Muslims: Same but different

The similarities between contemporary Islamophobia and 1930s anti-Semitism, in particular, are certainly striking: Panic about a Muslim "horde" coming from the east; an obsession with Muslim conspiracies against the West; and the generalized depiction of Muslim men as corruptors/abusers of vulnerable Christian women (from sex gangs in the north of England to the sexual assaults in German cities on New Year’s Eve 2016).

Open gallery view Protesters hold an anti-refugee, anti-Muslim banner during a rally, organised by far-right nationalists marking the 99th anniversary of Polish independence in Warsaw, Poland. November 11, 2017 Credit: AGENCJA GAZETA/REUTERS

If we replace the word "Muslim" with "Jewish," all of these racialized fears become rather familiar.

Yet the fundamental differences are also evident.

Geert Wilders might want to ban mosques in the Netherlands, but he does not call for Muslims to be expelled from Europe. Nor does he talk about Muslims wielding a hidden power that controls politics, finance, and the media, a widespread anti-Semitic trope in early 20th century Europe and now.

And we must not forget that the association between Jews and communism was a central part of European thinking about Jewry before and after the Second World War (John Le Carré’s first novel, "Call for the Dead," published in 1961, is testimony to its longevity). The idea of the Judeo-Bolshevik menace, however, has no corresponding concept in contemporary European debates about Islam.

The rivalry of theology

Nonetheless, the similarities between anti-Jewish and anti-Muslim racisms need to be explained. While a fear of Muslim power and wealth is not discernible in contemporary Europe, many Islamophobes do believe that a global Islamism is seeking to displace the Christian West.

Significantly, this phobia of a Muslim and a Jewish thirst for worldwide power was already apparent almost five centuries ago in Martin Luther’s "The Jews and their Lies," published in 1543.

The Jews, he argued, "want to have the Messiah and be masters of the world." Or, as he puts it another way, they wish to "fill their bellies and feast on the world’s joys" alone, and that is an ambition he declares Muslims hold in common. "[S]uch a mode of life [to possess all of the 'world’s joys'] Muhammad promises his Saracens [a 16th century term for Muslim]. In that respect he is a genuine Jew, and the Jews are genuine Saracens according to this interpretation."

Open gallery view A woman holding an umbrella walks by anti-Semitic graffiti on a wall in Kiev, Ukraine, June 5, 2006. Credit: AP

Of course, medieval and early modern Christian thought identified the Jews, the people of the Old Testament who rejected Jesus, as the primary enemy of Christendom, who were in league with the devil.

But after the birth of Islam in the seventh century, Christian theologians came to see both Muslims and Jews as heretics - corrupters of religious truth; or, to put it another way, rivals within the same Abrahamic monotheistic world. Jews and Muslims were regarded in similar fashion as obstinate, law-loving rejectors of Christ.

In an era in which theology and ideas of temporal power were intrinsically linked, the perceived religious competition between Judaism, Islam, and, indeed, different forms of Christianity, was understood as a struggle for political authority.

Of course, the idea of Islam as an enemy of Christendom was not confined to theology. With the rise of the Islamic empires, the Ottoman expansion into Europe and their capture of Constantinople, the Eastern Christian capital, in 1453, the military threat was quite real. Yet theology was the underlying source of the potency of the Christian fear of the Jew and the Muslim as existential enemies.

The rise of 'the Semites'

The conjoining of the Jew and the Arab Muslim in the European mind was made most explicit in the idea of "the Semites." The word "Semitic" was coined at the end of the 18th century, and was invoked as a label to group together peoples who spoke related languages in ancient Western Asia. The creation of the term belonged to the scientific endeavor to classify human groups according to linguistic-racial characteristics.

But the story of the Semites was not secular. The term derived from the name Sem, the Latin for Shem, who, according to the Book of Genesis, was one of the sons of Noah, and the ancestor of Abraham.

Open gallery view The shattered glass of the Muslim Cultural Center in Warsaw on November 27, 2017, after it was vandalized Credit: JANEK SKARZYNSKI/AFP

Since early medieval Christianity, the Bible’s genealogy of humankind after Noah wielded tremendous influence over how Europeans understood the origins of peoples. The descendants of Sem were thought to inhabit the desert lands of Western Asia, and included both Arabs and Jews. The Sem-ites were, according to the story, separate from the children of Japhet, who, many thought, became the peoples of Europe. For the language scholars of 19th century Europe, Japhet’s children became "Indo-European" or "Aryan."

Fundamentally, though, Europe’s ideas of the Jew and the Muslim were different, even though they were connected, precisely because of their theological roots.

The Jews, as the people of the Old Testament, were essential to Christian understandings of the world’s past, present, and future. In fact, Christianity was built on Judaism’s theological supersession by Christianity and their status as unredeemed heretics. Islam did not - and does not - hold the same significance for the Christian West.

Hence, within the notion of the Semites there was a fundamental imbalance, which made the idea of the Jewish-Muslim bond inherently vulnerable, if put under strain. This eventually happened, of course, with the conflict over Israel-Palestine that erupted in the 20th century.

Open gallery view Anti-Muslim campaign posters of the far-right Swiss People's Party:'Stop - Yes to the ban on minarets'. November 23, 2009 Credit: AFP

At this point, the idea of the Semites began to fall from grace. After World War II the refrain of a "Judeo-Christian" West came to prominence in its place. Today, the alt-right celebrate this so-called Judeo-Christian symbiosis as the defining feature of the West in its struggle against "world Islam."

Even so, the idea of the Semites was so enormously influential across Europe before it fell out of use that we must pay close attention to it. It was simply accepted as fact for more than a century that the Jew and the Muslim Arab were of one race. The Christian theological origins of this concept explains why it was of such influence for so long.

And this is why the ghost of the Semites is still with us. Europe’s far right discusses Muslims in ways that remind us of past anti-Semitism because these racisms come from the same source. This is not to say that Europe’s ideas of the Jew and the Muslim are the same. They are not. But they were, and are, intimately connected.

In 2017, anti-Semitism and Islamophobia in Europe are on the rise, in different ways. The idea of a global Jewish conspiracy is itself globalizing and has found a new incarnation with, for example, the vicious campaigns against financier and philanthropist George Soros.

Open gallery view File photo: Hungarian government poster portraying financier George Soros and saying "Don't let George Soros have the last laugh" is seen at an underground stop in Budapest, Hungary July 11, 2017. Credit: LASZLO BALOGH/REUTERS

And Muslims are targeted by European publics and governments as potential terrorists to such an extent that the very fabric of the liberal democratic state is being remade in the name of security. Trump’s serial anti-Muslim tweets belong to this mainstreaming of the image of Muslims as agents of violence.

Which racism is more virulent? Unfortunately, neither shows any signs of abating - quite the opposite. Perhaps that is the most significant testimony today of the legacy of centuries of Christianity’s preoccupation with Judaism and Islam: an unremitting global obsession with Jews and Muslims.

The shared story of Europe’s ideas of the Muslim and the Jew is complex. It has evolved over time and place, in the ages of Christendom, empire, and our postcolonial present. It is urgent that we grapple with this complexity and the implications for what should be today’s War on Racism.

James Renton is co-editor, with Ben Gidley, of "Antisemitism and Islamophobia in Europe: A Shared Story?" (Palgrave, 2017). He is reader in history at England's Edge Hill University and a visiting fellow at the European University Institute. Twitter: @RentonJE