In case you haven’t kept up, below is a very partial box score of global Islamist violence during the month of September:

Kenya: Militants of the Somali jihadist group Al Shabaab attack the upscale Westgate Mall in Nairobi, slaughtering visitors with grenades and machine guns, separating out some Muslims from non-Muslims, in a killing spree that ends three days later with an assault by the Kenyan military. Death toll: at least sixty men, women, and children, along with several soldiers and militants.

Somalia: Al Shabaab car and suicide bombers blow up the restaurant the Village in Mogadishu for the third time. Death toll: fifteen patrons and staff.

Pakistan: Suicide bombers detonate themselves outside a Protestant church in Peshawar. Death toll: eighty-five.

A remote-control bomb explodes on a bus carrying government employees near Peshawar. Death toll: nineteen.

A remote-control bomb explodes in an old, crowded marketplace in Peshawar. Death toll: thirty-seven.

Nigeria: Militants of the extremist group Boko Haram attack an agricultural college. Death toll: forty young male students, most of whom were sleeping when they were killed.

Iraq: Car bombings, suicide bombings, revenge killings, and assassinations reach levels not seen for at least five years. Death toll: nine hundred and seventy-nine. Wounded toll: twenty-one hundred and thirty-three, most as the result of Sunni-Shiite sectarian violence.

Syria: Al Qaeda-affiliated rebels tighten their grip across northern Syria, intimidating local residents with public floggings and executions.

Yemen: Militants from Al Qaeda in the Arabian Peninsula stage attacks on soldiers and police in southern Yemen. Death toll: at least thirty.

Afghanistan: Sushmita Banerjee, the Indian wife of an Afghan man, who converted from Hinduism to Islam and wrote a memoir about life under the Taliban which was later made into a Bollywood movie, is abducted from her home in Paktika Province, taken to a Taliban safe house, and shot twenty-five times. Two suspects are arrested and claim that they killed her because she had written about the Taliban, and because she had installed an Internet connection in her house.

Zanzibar: Attackers throw acid in the face of a Catholic priest as he leaves an Internet café, one month after two young British women were assaulted in the same way.

It was a very bad month. But the worst thing about September’s violence is how much of it was easy to ignore. The Westgate drama in Nairobi seized the world’s attention for a few days because it involved a glitzy landmark, a prolonged siege, and plenty of non-Kenyan victims. And yet scores, or hundreds, of people—shoppers, shopkeepers, worshippers, government workers, college students, housewives, children, most of them Muslims, none of them guilty of anything more than having been born in the wrong country—are being murdered every day, blown to pieces, burned alive, shot to death, beheaded, in the name of an extremely violent strain of Islam.

All this killing is taking place at a time when America is getting out of the Muslim world. There have been no troops in Iraq for almost two years. The U.S. military is drawing down in Afghanistan, and by this time next year there might be no American combat troops there, either, for the first time since 2001. The Syrian civil war has become a stage for foreign fighters from many countries, as America keeps its distance. Egypt’s political crisis is homegrown, with the White House just trying to keep up with events. The Israeli-Palestinian conflict remains a central concern of U.S. foreign policy and a source of grievances for Muslims (and others) around the world, but anyone who imagines that a resolution in the Middle East—or an end to drone strikes in Pakistan and Yemen, or the withdrawal of French troops from Mali, or an African Union drawdown in Somalia—would end the violence catalogued above isn’t thinking very hard about its causes.

American wars in Muslim countries created some extremists and inflamed many more, while producing a security vacuum that allowed them to wreak mayhem. But the origins of the slaughter are overwhelmingly internal—sectarian, tribal, political, economic. At its source, the violence flows from ideas, terrible ideas, about the meaning of Islam, the character of non-Muslims, and the duties of Muslims. These ideas are promulgated in mosques and coffee shops and schools, and on satellite TV and the Internet, with the aid of conspiracy theories, half-truths, deceptive editing, and lies. They are remarkably impervious to the ebb and flow of U.S. foreign policy.

Far from letting Americans off the hook, this realization puts us to a very difficult test.

When Islamist violence finally got Americans’ attention on September 11, 2001, the U.S. government responded in the simplest, most familiar way: with military power in tandem with intelligence operations. Twelve years later, Osama bin Laden is dead, Al Qaeda central is heavily damaged, and there’s been nothing close to a repetition of those attacks on American soil; but the wars were human disasters that failed to achieve most of their strategic goals. In the greater argument over prisoners, drones, security, and surveillance, Americans show far more interest in what their country does than what people do in Somalia or Pakistan. The verdict of the past dozen years is in: no more wars, including (according to the President) the one on terror.

This verdict still leaves a lot of room for armed American action overseas, as we saw over the weekend, with the abduction of a top Al Qaeda figure from the streets of Tripoli, in Libya, by U.S. commandos and intelligence officers, and a failed Navy SEAL raid on the stronghold of a Shabaab leader on the Somali coast. The Administration clearly regards the Nairobi mall massacre as a worrying sign of Al Shabaab’s desire and ability to hit soft targets around the world. But what about the kind of violence—like most of the incidents listed above—that doesn’t seem to threaten us directly? Why does this have to be our problem?

Some of the U.S. commentary on reports of last month’s violence took this thinking even farther: so let them kill each other. In the bipolar habit of America’s attitude toward the rest of the world, we’ve flipped from grandiose missionary zeal to sullen disengagement. The U.S. seems safer than it did on September 11th, the rest of the world less safe. Most Americans will take that trade-off.

While jihadism tends to start with the near enemy, however, there’s often a far and farther enemy. Every global jihadist group, including Al Qaeda, was born of a local conflict. It is an extraordinarily ambitious ideology. Beyond that, countries where suicide attacks targeting schoolchildren are common have a way of becoming the problem of their neighbors, and perhaps the world. It’s dangerous and dehumanizing when Americans grow inured to the regularity of mass shootings of innocents at home. Why should we be comfortably indifferent to Islamist violence against innocents abroad?

War turned out to be far too blunt an instrument against the complexity, volatility, and durability of Islamist violence. Targeted kidnappings and killings are effective against the leadership but do nothing about the next generation of recruits, perhaps only galvanizing it. And yet one approach that impatient, action-loving, results-oriented Americans have not given enough thought to is addressing the heart of the violence: the terrible ideas that license massacres in the name of religion. Americans are slow to believe in the importance of ideas—they seem like flimsy pretexts rather than root causes. The history of recent years and the news of the past month suggest otherwise.