I wasn't clear. I meant I'm not aware of a prior terrorist attack that was (1) so large
and (2) of an "armed assault" type.
I recognize that there are attacks by one or two gunmen, pretty often. But seems to be that, until now, the really big terrorist attacks have been via bombs - and airliner :-( (Excepting terrorist actions that are essentially part of ongoing wars, e.g. Iraq.)
Here is the most detailed article I've yet seen on how the Mumbai attacks were carried out.
http://www.longwarjournal.org/archives/2008/11/analysis_mumbai_atta.php
and an excerpt:
A unique attack
The Mumbai attack differs from previous terror attacks launched by Islamic terror groups. Al Qaeda and other terror groups have not used multiple assault teams to attack multiple targets simultaneously in a major city outside of a war zone.
Al Qaeda and allied groups have conducted complex military assaults on military and non-military targets in countries such as Iraq, Afghanistan, Chechnya, Somalia, Algeria, and Pakistan. But these are countries that are actively in a state of war or emerging from a recent war, where resources and established fighting units already exist.
Al Qaeda has also used the combination of a suicide attack to breach an outer wall followed by one or more assault teams on military bases in Iraq, Afghanistan, and Pakistan, as well as at the US embassy in Yemen. But again, these attacks are focused on a single target, and again occur where the resources and manpower is available.
Previous terror attacks in non-war zone countries such as India, London, Spain, the United States, Jordan, Morocco, and Egypt have consisted of suicide or conventional bombings on one or more critical soft targets such as hotels, resorts, cafes, rail stations, trains, and in the case of the Sept. 11 attack, planes used as suicide bombs.
The only attack similar to the Mumbai strike is the assault on the Indian Parliament by the Jaish-e-Mohammed, aided by the Lashkar-e-Taiba, in December 2001. A team of Jaish-e-Mohammed fighters attempted to storm the parliament building while in a session was held. A combination of mishaps by the terrorists and the quick reaction of security guards blunted the attack.
The Mumbai attack is something different. Foreign assault teams that likely trained and originated from outside the country infiltrated a major city to conduct multiple attacks on carefully chosen targets. The primary weapon was the gunman, not the suicide bomber. The attack itself has paralyzed a city of 18 million. And two days after the attack began, Indian forces are still working to root out the terror teams.