Three days after the Mumbai attacks, it is unclear who is behind them. And that in itself tells a story.
Terrorism experts have been all over television and the Internet speculating on the identity of the perpetrators, more often than not attempting to divine their identity from the group's tactics. The problem is that terrorists do not follow rule books; they learn and adapt from other groups. The fact that suicide bombers did not blow themselves up in the lobbies of the Oberoi or Taj hotels does not mean they are not from al-Qaeda. (See photos of the chaos in Mumbai)
What we should be certain of, though, is that the Mumbai attackers were combat trained. You do not sustain a military assault for three days, taking only combat naps, unless you know what you are doing. You have to have been shot at before. You cannot be intimidated by flash-bang grenades, or commandos fast-roping down the side of a building. And it is almost certain that the planners of the attack understood that the only way to get into India with the amount of weapons and explosives used in the attacks was by sea the risk of smuggling them in over land was too great.
Indulging in the same sort of speculation as the terrorism experts, I would say it's likely the attackers picked up their combat experience in Afghanistan. They could have come out of Iraq as well, but Mumbai seems a little far afield for Iraqis. Again, at this point none of this is certain. We may find out the killers were Hindu extremists, or Tamil separatists.
There are two lessons we should be taking away from Mumbai. The first is that all large cities are vulnerable to attack. Even if it doubled the size of its police force, there is no way New York City could could ever protect its hotels, schools or other public buildings from attacks of this type, short of turning them into fortresses. There is no way for the NYPD to prevent a car bombing on Wall Street, sending the stock market into an even worse plunge, or a single suicide bomber from blowing himself up in the subway. Plans are available on the Internet for making bombs like these with ingredients available in hardware stores.
The second reminder we should take from Mumbai is that the longer the wars go on in Iraq and Afghanistan, the more combat-experienced men there will be available to planners of terror attacks. And we should count on the veterans of Iraq and Afghanistan going global there is no reason they could not blend into the waves of immigrants crossing the Mediterranean from Northern Africa to Europe every day.
The best answer to the attack on Mumbai is a measured one: If it turns out the attackers came from Pakistan, they are very unlikely to have been sent by that country's government. So the last thing India should do is confront the government of Pakistan, or isolate it. That would only strengthen the hand of the extremists.