The murderous mission of the Somali rebel group al-Shabaab.
Din Hassan is standing by a petrol station in a densely packed Somali suburb of Kampala, the Ugandan capital. Since the suicide bombers attacked football fans while they were watching a World Cup match in bars just a few miles away, the residents of Kisenyi have been keeping their heads down. But Hassan smiles widely when he sees me and beckons me over. He is tall, with a round, bearded face and a belly that tests the limits of his grey safari suit. We cross the road and walk down an alley to his modest house.
Hassan was born here 64 years ago - "I am a Ugandan!" he says - but his grandfather grew up in what was then British Somaliland. Drafted into the army in 1909, the old man fought for George V against the Germans in Tanganyika (now Tanzania) before coming to Uganda as one of the original Somali settlers.
For most of the past 25 years, Hassan has been chairman of the Ugandan Somali community. His term coincided with Somalia's descent into chaos, which has swelled Uganda's immigrant population to about 40,000. "Ugandans have always been very friendly to Somalis," he tells me. "They know the people there are suffering."
By the time Hassan handed over to a younger chairman 18 months ago, relations between the two countries had become closely intertwined. President Yoweri Museveni of Uganda sent thousands of troops to Mogadishu in 2007 to help protect the fragile Somali government from the Islamist rebel group known as al-Shabaab. Many Ugandans wondered why they were getting involved in a country where there was no strategic interest. Hassan saw the move as honourable. "Museveni was just trying to help make Somalia like a normal country."
Al-Shabaab has a different idea of normality. Hassan first heard of the Kampala attacks when he arrived at a mosque early on the morning of Monday 12 July. He went straight home and stayed there. The death toll rose to 74. As families of the victims crowded around a tree outside the main hospital in Kampala, where a list of dead and injured had been pasted, al-Shabaab was holding a triumphant press conference in Mogadishu. A spokesman thanked "the mujahedins that carried out the attack", which he said was punishment for Uganda's role in the peacekeeping mission.
There was fear among the local Somalis: would Ugandans blame them for the bombings? Hassan's mobile rang constantly. "People were saying to me: 'You were our chairman for a long time. You must be the one to explain our position on this to the press,'" Hassan says. His expression hardens. "The people who did this are criminal killers. They have destroyed Somalia, and now they want to do something very bad to us here."
Something very bad - indeed, the most deadly terror attack in East Africa since the 1998 US embassy bombings in Kenya and Tanzania, which put al-Qaeda on the world map - could have been even worse. At the government media centre, a flimsy black canvas bag that was found in a disco sits on a table at the front of the room. Beside the bag are its contents: a piece of thin khaki material with orange trim and swatches of Velcro - a suicide vest. Next to it are two packets containing brownish slabs of explosive, roughly the size of a paperback, with blue electrical cord.
Some ball bearings have shaken loose from the explosive casing. When the bomb detonates, the ball bearings act like so many bullets; similar evidence has been recovered at the bars where many of last month's dead were torn to pieces. The device was probably meant to strike the disco at the same time, the police chief says.
Who are al-Shabaab? So far, the militants have brought order to the areas they control in southern and central Somalia. Some aid agencies there have complimented them on their administrative capacity. But most of al-Shabaab's professed values are deeply alien to Somali culture - and to Islamic norms in most parts of the world. Western songs, films and ringtones are banned. Men used to strolling around in sandals and sarongs as they chew the narcotic khat leaf are expected to grow beards and attend mosque five times a day, or face beatings.
Women who previously covered only their hair must now wear full face veils. Alleged criminals have limbs hacked off while local residents are forced to watch. Whatever the Somali government's faults - and the list is long - it is for fear of al-Shabaab that people risk their lives to reach countries such as Ethiopia, Kenya, Uganda and Yemen.
A short walk up the hill from Hassan's house is a modest hotel. In the restaurant, a few dozen Somali men are having lunch: rice mixed with potatoes, cabbage, raisins and large chunks of goat meat. The television is tuned to al-Jazeera.
I order some food and sit down. Eventually I strike up a conversation with the restaurant manager, Abdi Mohamed. He arrived in Uganda from Somalia in 2009. He says his reaction to the bomb attack was "like any Ugandan . . . scared. I was expecting to find peace when I arrived here." Mohamed knows all about al-Shabaab. His family lived in Kismayo, a port city in southern Somalia that is under the Islamists' strict control.
“If you are not one of them, it is very difficult," he says. "They are doing in Somalia what they have done here. Only 100 times more."