Why do Islamists kill each other? In the last three decades, Islamist rebels enmeshed in civil wars have descended into internecine conflicts that divided their ranks, alienated their supporters, and cost them their bid for power. From the Armed Islamic Group in Algeria, to al-Qaeda in Iraq, to the Islamic State, each of these movements had perfect opportunities to topple their regimes. Yet, in the midst of civil wars, they turned their guns on fellow rebels, choosing to pursue hegemonic leadership over coalition unity. In fact, they assisted incumbent elites in crisis by handing them the perfect opportunity to divide and conquer their movements. What explains this self-defeating behavior?

Fratricidal jihadists share three unique characteristics — or flaws — that make them prone to internecine wars. First, they frame their civil conflicts along Manichean lines, reducing the complexity of adversarial relations into categories of us versus them, good versus evil, Islam versus impiety. By doing so, they amalgamate their disparate enemies into a single united camp.

Second, fratricidal jihadists pursue transformative goals that are too ambitious for rebels with limited imaginations. Their doctrinaire ideology sacrifices all political realism, making them suspicious of kindred groups that might sell them out in the name of pragmatism. They prefer to wipe out their rivals than compete with them through political strategies.

Third, fratricidal jihadists usually begin as extreme factions that indiscriminately target civilians in their wars against a regime. Their ideological justifications generate a permissive moral code that allows for the killing of their own brothers in arms. Those who willfully justify the wanton killing of innocents will not find it difficult to turn their guns on fellow rebels who violate their notions of ideological purity.

Underpinning these recurrent strategic errors is a puritanical ideology impervious to accommodation with alternative worldviews. Jihadists often operate alongside militant factions that share some of their objectives but do not embrace their political ideals. They cannot even bring themselves to compromise with groups that share their political ideals but diverge with them on tactical pragmatism. Their puritanical ideology is also a major obstacle to strategic learning and adaption.They appear to be incapable of internalizing lessons from past failures, as evident from their proclivity to repeat mistakes even after being cautioned by veterans of earlier conflicts. These inherent weaknesses offer the international community strategic lessons for fighting future iterations of the Islamic State.

THE PUZZLE

In the last three decades, Islamist rebels have snatched defeat from the jaws of victory on three major fronts. During the 1990s, the Armed Islamic Group (Groupe Islamique Armé, GIA) saw the Algerian government mired in a legitimacy crisis after a military coup ended a popular electoral process. Rather than capitalize on the regime's internal vulnerabilities and international isolation, the GIA embarked on a fratricidal war with rival Islamists and alienated its supporters through mass atrocities. It lost the war and took down the entire Islamist project with it.

In the 2000s, al-Qaeda in Iraq (AQI) and other Sunni insurgents had the American-led coalition in a bind as the latter desperately sought a way out of a quagmire. Yet, like the GIA, AQI turned its guns on fellow rebels and sought to monopolize power at the expense of unity. Afterward, it was routed by the Sunni communities that once hosted its fighters.

The Islamic State is the latest jihadist group to fall victim to its own predation. It failed to learn the lessons of earlier jihads as it rebuilt its ranks in Iraq following the precipitous decline of its predecessor, the Islamic State in Iraq. Rather than seeking to forge unity with Syria's Islamist factions, it went its own way, by declaring a caliphate and waging war on fellow rebels. Today, it has lost the territory it once held in Iraq and is all but finished in Syria.¹

These three movements were well positioned to make gains against their regimes. At a minimum, they could have avoided the precipitous downfall they suffered at the hands of their adversaries, had they not turned their guns on fellow rebels. Yet, in the midst of their civil wars, they prioritized fighting with rivals above winning conflicts. In the process, they alienated their supporters, fragmented their movements and drove away external sponsors. More puzzlingly, they did not heed the warnings of veteran jihadists who communicated their concerns directly and clearly.