A masked man brandishes a severed head in one hand. In the other, he raises an index finger, a commonly understood symbol for the number one.

His name is Abdel Majed Abdel Bary, a failed London rapper turned jihadist, a British militant fighting for the Islamic State of Iraq and al-Sham (ISIS), also known as the Islamic State. British authorities suspect him of murdering American journalists Steven Sotloff and James Foley. In August, Bary posted a gruesome picture -- from a different killing -- on his Twitter account for the world to see.

The curious thing was not the head Bary held in his left hand -- however ghoulish the trophy -- but the gesture he made with his right. For followers of ISIS, a single raised index finger has become a sign of their cause, and it is increasingly common in photographs of militants. Some have even gone so far as to call the symbol “the jihadi equivalent of a gang sign.”

The Middle East and its upheavals are no strangers to gestures. Over the past year, a variety of groups, ranging from the Muslim Brotherhood in Egypt to the Kurds in Iraq, have used at least four distinct hand signals. These symbols communicate complex political messages that Western observers have largely ignored. That lapse is certainly understandable: next to a severed head, the number one is easy to overlook.

Yet gestures -- in particular ISIS’ index finger -- should demand far more attention. They are an important means by which regional groups communicate their core messages to viewers down the street and observers thousands of miles away in Europe and the United States. To understand the ideologies such groups aim to export, one needs to understand the symbols they use.

ISIS fighters in Syria, July 2014. Youtube

SIGNALS INTELLIGENCE

Gestures are as old as politics itself. They became especially important, however, with the advent of mass media in the twentieth century. Consider what is perhaps the best-known example: Adolf Hitler’s fascist salute. In a single gesture, Hitler communicated the power of National Socialism, the obedience of German crowds, and his own role as a supreme leader. And because pictures of him saluting were printed in newspapers around the world, the symbol reached billions.

Each subsequent advance in media technology has made it easier for political messages to reach mass audiences. But the Internet changed the rules of the game, democratizing the entire process of image making. Today, anyone with a cell phone can broadcast an image in an instant -- which is exactly what Bary did.

When ISIS militants hold up a single index finger on their right hands, they are alluding to the tawhid, the belief in the oneness of God and a key component of the Muslim religion. The tawhid comprises the first half of the shahada, which is an affirmation of faith, one of the five pillars of Islam, and a component of daily prayers: “There is no god but Allah, Muhammad is the messenger of Allah.”

It is no surprise, then, that the shahada features prominently in ISIS’ public image. The group’s black flag bears the vow’s words in white Arabic script (as does Hamas’ and even Saudi Arabia’s). And Muslims have long associated a single index finger with the shahada in a variety of contexts, ranging from daily prayers to conversions.

But for ISIS, the symbol is more sinister than a mere declaration of monotheistic beliefs. As Salafi jihadists, members of the group adhere to a fundamentalist interpretation of tawhid that rejects non-fundamentalist regimes as idolatrous. In other words, the concept of tawhid is central to ISIS’ violent and uncompromising posture toward its opponents, both in the Middle East and in the West.

When ISIS militants display the sign, to one another or to a photographer, they are actively reaffirming their dedication to that ideology, whose underlying principle demands the destruction of the West. If rank-and-file soldiers are aware of the precise theological implications of their sign -- and it would be no surprise if they are -- that would be a sobering comment on their deep-seated opposition to pluralism.

The gesture is equally important for what it means to Westerners, most of whom cannot read Arabic. By raising their index fingers, militants send an easy-to-understand message of the group’s goals of theological supremacy and military hegemony. When potential ISIS recruits in London, New York, or Sydney see the symbol on Twitter, they can grasp the scale of ISIS’ ambitions and its underlying aims. At some visceral level, less-radicalized viewers understand that it means dominance.

If ISIS has the solitary finger, its opponents have the so-called V-for-Victory gesture, popular among Iraqi soldiers and the Kurdish militia. Originally devised by the British Broadcasting Corporation as a sign of the Allied powers during World War II, the V has been used in the Middle East since its creation in 1941. At various moments in history, a wide array of groups has appropriated the symbol, among them Palestinian terrorists, Iranians who took part in the failed “green revolution,” and Egyptians in Tahrir Square.

As the diversity of its devotees suggests, the V has less rigidly defined political dimensions than the raised finger. It is a general symbol of defiance, protest, and self-expression without intellectual meaning. (The V is so generic, in fact, that supporters of ISIS have also displayed it in photographs.) But in some ways, the use of the V cuts to the core of what the opposition to ISIS is all about -- a collection of factions with differing aims and worldviews bound together only by a fear of the Islamic State. Whereas ISIS’ followers are unified by fundamentalist ideals, its opponents are not equally united.

A Kurdish woman making a victory sign in Turkey, December 2009. Umit Bektas / Courtesy Reuters

FREEDOM OF GESTURE

ISIS and its opponents are not the only groups in the region making use of gestures. Two other symbols have been visible in the region over the past year, and they provide important context for ISIS’ index finger signal.

One gesture emerged when Hamas operatives kidnapped three Israeli teenagers last July. Palestinians celebrated the news by jubilantly thrusting three fingers in the air, one for each of the hostages Israel would have to ransom by releasing convicted terrorists from jail. Called the “three Shalits,” after the IDF-soldier-turned-hostage Gilad Shalit, the symbol quickly spread across the Arab world via social media, in many cases with young children posing for the camera and proudly showing three fingers.

As with ISIS’ signal, this new gesture’s intended message was easy to comprehend: ordinary Palestinians supported Hamas and its tactics. However, where Western media has been slow to identify the significance of ISIS’ sigil, the Israeli press and some U.S. media outlets quickly highlighted the meaning and implications of the “three Shalits.” At one level, the difference in responses is not surprising: the pro-Hamas symbol appeared across the West Bank and was a more immediate concern to Israel, physically and politically, than ISIS’ gesture seems to be to the West.

The second symbol, championed by the Muslim Brotherhood in Egypt, was widespread a year ago, but has since begun to disappear. Last summer, Mohammed Morsi, who was president of Egypt, clashed with the country’s army in a contest that ended with his fall from power. In one incident, the army killed hundreds of Morsi’s followers at the Rabaa al-Adawiya mosque. The word Rabaa means “four” in Egypt, and the Brotherhood quickly adopted a four-fingered hand gesture as its symbol.

In rallies from Cairo to Istanbul, Brotherhood supporters held up yellow signs with a Rabaa hand-gesture printed in black, wore Rabaa buttons, and made the signal with their own hands. It was an attempt to remind Egyptians and the world of the Army’s massacre and shift the narrative away from Morsi’s failed democratic promises.

Since the Egyptian army deposed Morsi, it has worked hard to quash the Rabaa, banning the country’s Olympic athletes from making the gesture in Sochi this past winter. The Brotherhood’s supporters, meanwhile, have tried to keep it alive, hosting a worldwide “Rabaa day” this past August. The army’s efforts seem to be paying off, as the gesture and its underlying message are petering out somewhat from the international stage. If the Rabaa is a bellwether for the health of the Muslim Brotherhood, don’t bet on the group returning to power any time soon.

For governments in the West, the Rabaa should raise an important question: When ISIS’ index finger reaches their shores, do they follow the Egyptian model of suppression? Or do they honor principles of free expression? Dilemmas of free speech, of course, are nothing new. European authorities have grappled with a similar question with regard to the so-called quenelle, an anti-Semitic gesture that resembles a reversed Hitler salute. French officials have taken a hard line, attempting to bar the comedian Dieudonne M’bala M’bala, who invented the quenelle, from performing in the country. The French Football Association has disciplined soccer players for displaying the quenelle in matches. But it seems that attempting to suppress the gesture has been far from effective, turning Dieudonne into a martyr for free expression.

A Morsi supporter waves a flag bearing the Rabaa, May 2014. Mohamed Abd El Ghany / Courtesy Reuters

Middle Eastern gestures, meanwhile, have already made their way west. In some cases, they have met with censorship: Facebook took down a public group that encouraged users to upload photos expressing support for kidnappings carried out by Hamas with a three-fingered salute. If any gesture were to be banned, it would be the raised index finger, which already cropped up at a pro-ISIS rally in The Hague at the end of July. However, measures to criminalize ISIS’ hallmark would, as in the case of the quenelle, likely backfire, turning ISIS supporters into victims of censorship.

At the very least, Westerners need to become more attuned to what the gesture means. It is doubtful that most Dutch citizens understood the radical ideas behind the raised index fingers in The Hague, and one could say the same of publics in other Western countries. Their continued ignorance will only make it more difficult to evaluate the threat ISIS poses in the Middle East.

ISIS’ single raised digit, so seemingly inconsequential at first blush, is a statement about the group’s diametric opposition to a liberal world order. Its use is all the more troubling in the hands of Western-born Jihadists with the passports to travel outside the Middle East. Indeed, those who underestimate the dangers posed by the Islamic State need look no further than the index finger, which makes ISIS’ ambitions all too clear.