While Pakistani Islamic terrorists are fleeing to Karachi, a major port and the largest city in Pakistan, Afghan bandits and Taliban are fleeing into Pakistan, and causing something of a crime wave. The movement of Pakistani Taliban to Karachi was is seen as an indicator that many terrorists were going to be quiet for a while because there were so many Pakistani soldiers in the tribal territories. That would be welcome to most Pakistanis. In the last year, there has been a sharp increase in Islamic terrorist bombing in Pakistan, but nearly all of them have taken place in the tribal territories (in the west and northwest, along the Afghan border). Nearly all the terrorists are Pushtun tribesmen, or al Qaeda foreigners (from Arab nations, Central Asia or Chechnya). In the last 15 months, the Pakistani armed forces has gone to war, with over 100,000 troops converging on the tribal territories, killing thousands of Taliban gunmen, and scattering the terrorist militias that, earlier in the year, considered themselves invulnerable. Taliban safe houses and weapons storage sites have been captured, and police and soldiers are going door to door looking for senior Taliban members. Naturally, one would expect most Taliban to flee for the hills, or to visit distant kin, and wait out the Winter, and, hopefully, the army offensive. The army has reduced its activity in the last few months, and established truces with the local Taliban and other terrorist groups.
There have been few truces with the Afghan bandits and terrorists fleeing across the border. Afghans fleeing to Pakistan have been a problem since the 1980s. But back then there was lots of money from Islamic nations (especially Saudi Arabia) meant to make life more comfortable, or at least tolerable, for the Afghans. There was also sympathy, as the Afghans were fleeing the violence of the invading Russians. Moreover, those refugees included lots of women and children. The current crew tend to be armed men chased out by police and soldiers. American air power has been particularly unforgiving of groups of armed Afghan civilians. This time, the fleeing Afghans found no welcoming government, but rather tribesmen and soldiers who were hostile to armed illegal migrants. The new guys reacted by foraging to survive, and killing those who refused to be generous.
Meanwhile, the hundreds of Taliban who fled to Karachi arrived in a city that is home to over two million Pushtuns (out of a city population of 12 million). About half these Pushtuns are Afghans (refugees from the 1980s war with Russia) and their children. Since Pushtuns, as a group, are ill equipped for urban living (low literacy, and few technical skills), most are poor. The low rent neighborhoods are full of Pushtuns, who are also overrepresented in criminal gangs. But the Pushtuns are closely watched by the police, and have earned some peace by not encouraging or supporting terrorists. Whenever this understanding is violated, as it is from time to time, the police lock a lot of people up, and even expel Afghans from the country. This last threat is much feared, and there's really no way to protect yourself from it, other than having done the cops some favors in the counter-terrorism department.
So the fleeing Taliban can expect shelter in Karachi, but not a new base from which to plan and carry out more terrorist attacks. This has always been a great fear among non-tribal Pakistanis (80 percent of the population). The non-tribal majority in Karachi, even those who are Islamic conservatives, will turn in suspicious Pushtuns quickly if they suspect terrorism. The recent flood of cell phone service into the city has made that much easier, and the terrorists know it. The police also know that the Taliban are in Karachi, and are out looking for them. But as long as these beaten Taliban keep their heads down, they will be hard to find. Meanwhile, the police have lots of more obvious Afghan Taliban entering the country.