The seven years since the September 11 attacks have been remarkable for the absence of any truly major or significantly innovative terrorist attacks on par with that day's heinously tragic events. Last Wednesday evening's coordinated terrorist attacks in Mumbai, India have likely changed that. To be sure, since 2001 there have been bombings in Bali, Istanbul, Madrid, and London among other places; but the vast majority of terrorist incidents seemed to be confined to established zones of conflict like Israel/Palestine, Iraq, Afghanistan and more recently, Pakistan. For the past two years, India has also been repeatedly targeted by terrorists-for instance, the July 2006 commuter-train bombings also in Mumbai, that claimed more than twenty lives and injured scores of others, and the series of unrelenting and unexplained low-level bombings that have convulsed the country's markets, train stations, restaurants and other public gathering places that have steadily driven up the death toll to some two hundred persons. But the Mumbai attacks were of a completely different magnitude and intensity. And, they are likely to exert a profound influence on future terrorism patterns.

In the United States, there's a clear continuing risk from lone gunmen or home-grown extremists. America's most recent massacre-the April 2007 shootings at Virginia Tech, which claimed the lives of more than thirty persons-is testament to that. The 2007 plot by six self-identified Islamic militants to attack Fort Dix, New Jersey is another case in point. But while authorities must continue to worry about attacks by "amateur" or wannabe terrorists like these, their focus-preparations and response capabilities-will inevitably have to be geared to the more "professional," trained, disciplined and deployed terrorists, as it is doubtful that home-grown terrorists could amass the numbers and have the requisite skill-set required to hit multiple target sites with the ferocity that the Mumbai attackers exhibited.

Indeed, beyond any doubt, the Mumbai operation was planned, premeditated and executed by terrorist teams functioning under a command and control apparatus that orchestrated their deployment and coordinated their assaults. In this key respect, the attacks diverge significantly from the pattern of a lone suicide bomber entering a hotel ballroom or riding a subway car and blowing himself up, or of simple home-made bombs surreptitiously planted hours before they explode and triggered from a distance by timed or remote-control detonators.

Mumbai saw disciplined teams of well-armed, well-trained terrorists simultaneously spreading throughout the city to execute their mission at least ten different targets. In each case, they stood their ground and inflicted the carnage and bloodshed they were doubtless trained to accomplish. And, in the cases of the assaults on the Taj Mahal Palace & Tower and Oberoi hotels, not only effectively resisted counterattack by Indian security forces, but impeded and inflicted serious losses on those forces-including the deaths of the city's top police counterterrorist commanders.

The attacks demonstrate how a small number of armed and trained terrorists can paralyze a city, stymie the security force, undermine public confidence in the ability of government and the authorities to respond, and generate worldwide attention and publicity. The lesson of how easily India's premiere financial capital and economic center can be brought to a standstill, and the immense challenges of responding to multiple, coordinated urban assault will likely preoccupy federal, state and local authorities in the United States and elsewhere in the months and years to come.

Bruce Hoffman is a contributing editor to The National Interest and a professor at Georgetown University's School of Foreign Service. He is also the author of Inside Terrorism (2006).