ISLAMABAD, Pakistan -- The torrent of intelligence that led to dozens of arrests in Pakistan and Britain and a terrorism warning in the United States began with a hunt for those behind an audacious ambush in June on a Pakistani commander as his motorcade tried to cross Karachi's Clifton Bridge.
The trail has led from the teeming streets of that southern port city, to the dusty tribal village of Shakai along the Pakistan-Afghan border, to seemingly placid suburban London, to the world's financial headquarters in New York, and to Washington, D.C.
The arrests of several senior Al Qaeda figures in Pakistan and Britain in the weeks that followed -- including a key operative in London and a man on the FBI's most-wanted list for the US Embassy bombings in East Africa -- are a striking example of intrepid police and intelligence work, international cooperation, and simple good luck.
The breaks have dealt a significant blow to Osama bin Laden's network, eliminated a tribal transit point for his men and drawn the strongest link yet between Al Qaeda's international plans and attacks on senior politicians here, including President Pervez Musharraf and the prime minister-designate, more than half a dozen Pakistani police and intelligence officials said.
What they haven't done, officials warn, is eliminated the Al Qaeda threat or prevented leaders such as bin Laden from organizing attacks.
''This is a network that we are trying to break. It is in the process of being dismantled," Interior Minister Faisal Saleh Hayyat said in an interview yesterday. ''But the network is still not finished."
The gunmen escaped after the June 10 attack on Ahsan Saleem Hayat, Karachi's top general, but police traced them through a stolen van found abandoned and bloodstained later that day. The general escaped unharmed; 10 other people died in the attack.
The van's owner gave police a description of the men who had stolen it, and that led them to a militant hideout in Karachi where on June 12 they arrested nine people, including alleged ringleader Atta-ur Rahman and another man, a young Pakistani named Shahzad Bajwa.
The men, part of a previously unknown group called Jundallah, or Allah's Brigade, are also believed to have been involved in recent attacks on Shi'ite Muslim mosques in Karachi.
Both Rahman and Bajwa received training in October and November of 2003 in South Waziristan at an alleged Al Qaeda facility and shooting range on the property of tribal leader Eda Khan.
The camp near Shakai, a town of mud-brick compounds surrounded by mountains and forests, was overrun by the army in June following the arrests in Karachi. Eda Khan surrendered and is in custody.
On June 12, police and intelligence agents in Karachi also arrested Masrab Arochi, a nephew of Al Qaida's former number three, Khalid Shaikh Mohammed, and a suspected terrorist operative himself, Hayyat said.
Hayyat said Arochi, Rahman, and Bajwa had all been to Shakai, which he described as ''a major transit point" for Al Qaeda figures.
''They received their training in Shakai," the interior minister said. ''Shakai is an area where -- when we finally overpowered these elements and flushed them out -- we found that it was being used as a training ground by Al Qaeda."
Pakistani intelligence officials say the CIA cooperated in the Arochi arrest, as well as those that followed.
Arochi's family has long ties to terrorism. He is a cousin of Ramzi Yousef, who was convicted in the 1993 World Trade Center bombings and is serving a life sentence in the United States.
The government has failed to produce Arochi in court. Hayyat was circumspect about his connection to other Al Qaeda figures, but three intelligence officials said on condition of anonymity that he led police to a network of other alleged operatives, including Mohammed Naeem Noor Khan, a 25-year-old computer specialist arrested July 13.
The arrest of Khan was a breakthrough -- revealing a terrorist web that stretched far beyond Pakistan's borders, officials say.
His computer had coded e-mails to many other Al Qaeda operatives, as well as photographs of Heathrow Airport and other potential terrorist targets in Britain and the United States, according to a Lahore-based intelligence official.
Khan used to frequently visit Wana, the main town in South Waziristan, the intelligence official said, and he was married there to the sister of a ''top-ranking" Taliban leader. The official said Khan had been to Britain four times, always on reduced price tickets he got through his father, a flight attendant with Pakistan International Airlines.
Khan helped lead authorities to Ahmed Khalfan Ghailani, a Tanzanian with a $25 million US bounty on his head for his role in the 1998 embassy bombings.
Information taken from Khan and Ghailani's computers was shared with British authorities, who on Tuesday conducted a sweep in and around London that netted 13 suspects, including a man known as Abu Eisa al-Hindi or Abu Musa al-Hindi. One man was later released.