The district of Hodan, in Mogadishu, the capital of Somalia, exemplifies the city’s transformation in recent years. Visitors can find open-air pizza restaurants, ice-cream parlors and shisha bars, hotels and restaurants, barrow boys hawking bananas and mangoes, and taxis and cars honking their way through the throng. Pretty much every day is busy, but Saturdays are especially so. This past Saturday, a massive truck bomb detonated in Hodan, killing more than three hundred people, an unprecedented death toll in Somalia which may rise as bodies are hauled from the wreckage.

The blast caused the multistory Safari Hotel to collapse, partially demolished nearby buildings, and mangled vehicles that were parked on the street. The aftermath of the attack was reminiscent of the worst of the years of the civil war that has ravaged Somalia since 1991. The city’s Aamin Ambulance service, which for the last decade has been among the first to respond to bombings, tweeted, “We haven’t seen anything like this.”

No one has claimed responsibility for the attack, but suspicion focussed on Al Shabaab, an Al Qaeda-aligned militant group that has been fighting successive Somali governments for a decade. Saturday’s bombing came after months of relative peace in Mogadishu, which had made it feel as if Somalia had turned a corner in its long and turbulent history of state collapse.

“Everyone is shocked that Shabaab can conduct such a ferocious attack in the heart of a government-controlled district,” Rashid Abdi, the Horn of Africa director at the International Crisis Group, in Nairobi, told me. Civilians in Mogadishu, especially ones participating in commerce—or, worse still, fun—are, for Al Shabaab, considered legitimate targets and careless collateral. “Shabaab has shown no concern for civilians,” Abdi said. “It sees the population as being on the government’s side, so an attack in the bustling heart of the city is not a problem for them.”

Small-scale bombings and attacks in Somalia—and elsewhere in the region—that kill dozens of people have become routine, but a death toll in the hundreds is remarkable. The sheer scale of Saturday’s attack pointed to Al Shabaab’s increasing sophistication in bomb-making, a willingness and ability to cause mass civilian casualties, and the failure of the internationally backed government to provide basic security.

Al Shabaab’s insurgency grew out of the Islamic Courts Union, a grassroots Islamist alliance that defeated the clan warlords who carved up and fought over the country after the dictator Siad Barre was overthrown, in 1991. The United States backed an Ethiopian invasion, in 2006, which shattered the Islamic Courts Union, leaving its armed wing, Al Shabaab—which means “the Youth”—to launch a guerrilla resistance that has lasted more than a decade and grown increasingly extreme.

Outside of Somalia, Al Shabaab has bombed soccer fans in Kampala, attacked shoppers and students in Kenya, and recruited fighters from among disenfranchised young people across the region. In Somalia, it has staved off the Islamic State’s attempts to gain a foothold and made its signature marauding attacks, in which suicide car bombers backed by small squads of gunmen attack military, government, and civilian targets. It has also displayed a remarkable capacity for adaptation and persistence. Until Saturday, its deadliest domestic attack had been a suicide bombing, in 2011, that killed more than a hundred students as they lined up to apply for international scholarships.

The new government of President Mohamed Abdullahi Mohamed—a dual Somali-American national known by his nickname Farmajo—has sought to impose a “ring of steel” security strategy in Mogadishu since his election, in February. “The aim is to push the perimeter out and harden it, to make it more difficult for Shabaab to penetrate the city,” Matt Bryden, the director of Sahan Research, a Somalia-focussed think tank in Nairobi, told me. With fewer bombings in recent months, the strategy appeared to be working. “The message is clear: Shabaab is still in business,” Bryden said. Al Shabaab has been building ever-larger truck and car bombs, and the attack was “sadly predictable,” Bryden added. “The scale is out of the ordinary, but the method is familiar.”

The attack came as Farmajo’s government is increasingly beset by internal division. The fortunes of the state and Al Shabaab are closely linked—when one is weak, the other is strong. Farmajo looks weak. The new President’s decision, in late August, to extradite a commander of the Somali separatist Ogaden National Liberation Front to Ethiopia was widely condemned as appeasing an old regional enemy and betraying nationalist principles. It bolstered Al Shabaab’s claim that it is the true defender of Somali nationalism.

Reuters reported last month that rival units of the Somalian military engaged in a deadly gun battle in Dayniile, an outlying district of Mogadishu. Last week, the country’s defense minister and Army chief both resigned. “We have seen weeks of internal schisms in government, especially in the security sector,” Abdi said. “Shabaab exploits these situations.”

The international powers that back Farmajo’s government, and pay for the twenty-two-thousand-strong African Union force that defends it against Al Shabaab, issued statements of outrage, sympathy, and support after Saturday’s bombing. “Such cowardly attacks reinvigorate the commitment of the United States to assist our Somali and African Union partners to combat the scourge of terrorism,” the U.S. Mission to Somalia said in a statement.

For years, the American military has been engaged in a covert war in Somalia. American drones and missiles have killed two successive leaders of Al Shabaab (Aden Hashi Ayro, in 2008, and Ahmed Abdi Godane, six years later), as well as dozens of lower-ranking commanders and hundreds of fighters. But decapitation has not eliminated the group.

Since taking office, President Donald Trump has loosened restrictions on U.S. military action in Somalia, designating parts of the country an “area of active hostilities,” which has increased the frequency of U.S.-backed raids. In May, a Navy SEAL was killed during a raid, the first combat death of an American soldier in Somalia since 1993, when eighteen U.S. servicemen died fighting in Mogadishu during a battle made famous by the book and film “Black Hawk Down.”

Somalia now rarely attracts American attention. A famine in 2011 that killed two hundred and sixty thousand people sparked a sweeping but belated international humanitarian effort, and this year, when drought struck again, the worst hunger was forestalled. But responding to acute crises is simpler than solving chronic ones, such as rebuilding the Somali state after decades of civil war and famine.

Al Shabaab is just the latest iteration of several generations of nationalist Islamist resistance movements in Somalia. Though neither monolithic nor entirely cohesive, the group has shown a tenacity, perseverance, and unity of purpose that has humbled a succession of foreign-backed governments, which have crumbled under the weight of clan divisions, corruption, and incompetence. As Somalis bury their dead, the government has declared three days of mourning. The world’s attention will likely have moved on before they’re over.