September 11, 2001 was not an inexplicable act of violence. The men who carried out the attacks belonged to an ideological tradition that had identified the United States and the broader West as enemies long before commercial airplanes were hijacked that morning.
Twenty-five years later, the danger is that Americans remember the horror of 9/11 while forgetting the ideas that helped produce it. Those ideas have a history, a doctrine, and adherents who did not disappear with the men who carried out the attacks, nor are they confined to the history of that day.
Faith has repeatedly served as a catalyst for organized conflict, and pretending otherwise leaves Americans unprepared for actors who still treat Western civilization as a legitimate target.
Religious war is not an Islamic enterprise. Charles Martel halted a major Umayyad raid at Tours in 732. The Reconquista, spanning centuries, ended with the fall of Granada in 1492. In 1683, Polish King John III Sobieski’s cavalry charge helped lift the Ottoman siege of Vienna. But Europe itself spent generations tearing itself apart in intra-Christian wars of religion. These episodes show that conviction, when fused with political power and a sense of sacred duty, can drive expansion, reconquest, and slaughter. The relevant question on the anniversary of 9/11 is not whether religion can motivate violence—it can—but whether a particular political-religious ideology still regards the West as territory to be subordinated.
Dar al-Islam, Dar al-Harb, and the philosophy behind the threat
Classical Islamic jurisprudence developed a territorial distinction: dar al-Islam (the abode of Islam), where Muslim authority prevails and Sharia is applied, versus dar al-harb (the abode of war), lands not under that authority. Modern reformers and many Muslim-majority states treat the old binary as obsolete in an era of nation-states and international law. Jihadist and Islamist currents do not. They keep the framework alive by treating Western civilization as a decadent domain of unbelief whose laws, culture, and power must ultimately yield.
The distinction between dar al-Islam and dar al-harb can be internalized as personal piety and spiritual struggle or externalized as a civilizational project where violence—converting by the sword—is an imperative. The latter version treats Jerusalem, Athens, and Rome—the sources of biblical ethics, Greek reason, and Roman law that formed the West—as deadly rivals. Just because many Americans no longer think in those terms does not mean others have stopped.
Why Arab states banned the Muslim Brotherhood
The Muslim Brotherhood, founded in Egypt in 1928, is not a vague “Muslim group.” It is a political movement whose slogan has long been that Islam is the solution and whose goal is comprehensive Islamic governance. It has combined social work, electoral participation, and, in various branches and offshoots, violence. Hamas began as its Palestinian arm. Several Arab governments that know the region from the inside have designated it a terrorist organization or banned it outright: Egypt after the 2013 ouster of Mohamed Morsi, Saudi Arabia and the UAE in 2014, and Jordan in 2025 after authorities alleged a plot involving weapons and sabotage. These regimes are not liberal democracies. They banned the Brotherhood because they viewed it as a subversive challenge to their own authority—an organized political Islam that uses popular piety to contest the existing order, sometimes through the ballot box and sometimes through violence.
The threat that remains, even when it is quieter here
Al-Qaeda planned 9/11. Its offshoots and the Islamic State persist. IS and affiliates remain among the deadliest terrorist organizations globally, with a pronounced shift of activity toward Africa. Al-Qaeda’s Sahel franchise JNIM has grown. Lone actors and small cells inspired by these groups continue to appear in the West. The absence of another spectacular attack on the scale of 2001 is a hard-won counterterrorism success; it is not evidence that the underlying deadly ideology evaporated. Groups that still speak of caliphate, apostate rulers, and the duty to confront the far enemy do not require majority Muslim support to kill. They require sanctuary, narrative, and recruits.
The red-green alliance and its contradictions
A working coalition has formed between segments of the radical left and Islamist movements. They share enemies: the United States, Israel, liberal democracy, and the existing international order. They do not share an end-state. One side wants revolutionary equality and fluid identity; the other wants Sharia and a restored ummah—the global Muslim community. History suggests the Islamists are not confused about which vision wins if they ever hold power. Iran’s leftists learned that hard lesson after 1979 after thousands were executed. “Queers for Palestine” makes as much sense as “Turkeys for Thanksgiving.”
None of this requires treating 1.8 billion Muslims as a hive mind. Most are not jihadists. Many live in the West, serve in its militaries, and reject political Islam. Arab governments that banned the Brotherhood did so because they distinguished ordinary faith from a revolutionary project. Americans can do the same without sliding into either blind denial or the sort of collective blame quickly labeled as Islamophobia.
In the mid-1980s I studied Arabic and spent a semester at the American University in Cairo to learn Islamic political thought on its own terms. The civilization is deep; the political currents that treat non-Muslim rule as illegitimate and the West as a field of struggle are also real. Twenty-five years after four hijacked jetliners hit the Twin Towers, the Pentagon, and an open Pennsylvania field, the reminder is simple: an ideology that still names Western civilization as dar al-harb will keep producing people willing to commit heinous acts of violence in service of a belief. Understanding this is not bigotry and defending our way of life is not optional.