Terrorist attacks like the one that killed over 300 people in Sri Lanka will always carry a degree of the unknowable. The psychology that leads someone to participate in mass murder is too individual, and too proximate to insanity, to be fully understood.

And the strategic narratives of such attacks — which group for which cause against which perceived enemy — are notoriously muddy, with various organizations often issuing criss-crossing claims of responsibility and intent.

But we have been struck by the fact that one aspect of these attacks is hardly questioned anymore: the notion that “terrorism” is the indiscriminate mass murder of civilians conducted less for any concrete strategic aim than out of fuzzy ideological fervor or pure nihilism.

That absence of clear meaning or strategy — once a shocking, destabilizing idea — is now treated as a matter of assumption. As simply how this works.

It’s easy to forget that this is a relatively new kind of violence. Maybe 20 or 30 years old, depending on how you date it, and still taking shape.

That it has now extended to Sri Lanka — a South Asian island nation far removed, physically and politically, from the usual flashpoints of this new terrorism — just underscores how global a phenomenon it has become. That kind of terrorism is no longer particular to the certain conflicts or ideological movements, principally in the Arabic-speaking Middle East, from which it first arose. It’s now universal.

Terrorism — the use of targeted violence against civilians to achieve some political aim — is hardly new, of course. But it had typically followed a logic much more closely resembling that of an insurgency or conventional armed conflict.

Consider, for example, Northern Irish groups that bombed civilians as part of a campaign intended to pressure Northern Irish unionists and the British government into accepting Northern Irish independence from the United Kingdom. Or Palestinian groups that hijacked airliners to try to advance the cause of Palestinian independence. Both were common in the 1970s and 1980s.

Contrast that with the newer kind of terrorism. For example: the 2015 Islamic State suicide bombing of a Shia mosque in Kuwait, an attack whose strategic rationale was far more amorphous. To punish Shia, as a global community, for having the wrong views? To fulfill vague jihadist dreams of a genocidal, end-of-times conflict?

Or consider, a few months later, the Islamic State attacks in Paris, in which  militants killed 130 people. While the group would claim it had sought certain objectives — an end to Western involvement in Syria, for example — it’s difficult to fully explain the attacks on those grounds, given how little French civilian targets had to do with mostly-American military forces. And besides, the group’s internal propaganda suggests it was motivated just as much or more by grander and vaguer ideological aims. It was civilizational conflict for the sake of civilizational conflict, given the veneer of strategic intent after the fact.

The attacks in Sri Lanka are the latest sign that this kind of terrorism is expanding well beyond traditional jihadist causes and communities. This island nation and its politics have very little to do with jihadist causes.

But it’s not just Sri Lanka. Indiscriminate, nihilistic terrorism, initially associated with Arabic-speaking Islamists, is increasingly being adopted by a new strain of white extremist. There was Dylann Roof, the American who murdered nine people at a predominantly black church in Charleston, S.C. in 2015. And there was the Australian man who killed 50 people at two mosques last month in Christchurch, New Zealand.

Those attackers emerged from a particular strain of white extremism, which blends old-style white supremacism and white nationalism with the anti-social anger of certain niche social media networks. But the methodology of their attacks draws from the same new kind of terrorism that we saw in Sri Lanka.

The increasing universality of this kind of terrorism should lead us to question our longstanding assumption that it was particular to Islamist extremism.

It’s true, as the scholar Will McCants has written, that the Islamic State drew heavily on extreme forms of an apocalyptic millenarianism that had some roots in Islamic theology. That belief in a cleansing, world-ending conflict absolutely informed the group’s embrace of indiscriminate mass murder. Religion didn’t have nothing to do with the kind of violence they adopted.

But it’s maybe more important to see how that movement, and predecessor movements that first developed this kind of terrorism, emerged out of specific conflicts and political contexts that just happened to play out in Arabic-speaking, mostly Muslim societies between the 1980s and 2010s.

Bruce Hoffman, a scholar of terrorism, has traced the genesis of spectacular mass attacks to the 1983 truck bombing of American and French barracks in Lebanon by the Lebanese militant group Hezbollah. The attack was conventional in its aims — to pressure the Western governments to withdraw their forces, and it succeeded. That success inspired other groups in the region to take up large-scale bombings as a tactic.

First that meant Palestinian groups that used bombings, including against civilians, to advance their conflict with Israel. Islamist militants later carried those tactics into civil wars in Algeria and Afghanistan.

Some Arab fighters returned home with grander ambitions. Al Qaeda conducted mass-scale attacks whose stunning spectacle was part of the point. But the goals remained, if outlandish, earthly: the withdrawal of the United States from the Middle East and collapse of allied Arab dictatorships.

When those same groups and individuals rushed into Iraq after the 2003 American-led invasion, something changed. The logic of spectacular terror attacks meant that whoever spilled the most blood would win the most attention and therefore recruits. That competitive outbidding favored the nihilists and the true believers in bringing about the apocalypse — men like Ahmad Fadhil Nazzal al-Khalaylah, a Jordanian veteran of Afghanistan better known by his nom de guerre, Abu Musab al-Zarqawi.

It was Zarqawi, and his un-strategic embrace of mass killing for its own sake, violence so extreme that it alienated even Al Qaeda, who introduced, in the chaos of mid-2000s Iraq, the nihilistic violence that we equate with terrorism today.

Zarqawi’s group in Iraq later became the Islamic State, whose claims of responsibility for the attack in Sri Lanka may or may not turn out to be true. But, regardless of whether it had any role, the kind of terror that Zarqawi and his successors pioneered has become part of the fabric of our world.