The Pebble and the Avalanche

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Current Revolutions in Business and Technology

by Dr. Moshe Yudkowsky,

author of The Pebble and The Avalanche: How Taking Things Apart Creates Revolutions


Sun, 2008-Nov-30, 18:57

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Casualty Ratios in the Mumbai Attacks

My friend and colleague Bruce Schneier asked me about the Mumbai attacks — in particular, the "low" number of casualties per terrorist. Based on current information, the ratio of fatal casualties per terrorist seems to be in the range of 10 to 30 per terrorist (at the high end, assuming 10 terrorists and 300 fatalities). Given that the siege lasted a long time, that the venues of the attacks were undefended, and that the victims were unarmed, wouldn't we expect more causalities? (See slide 15 in this presentation; a complex attack such as the Mumbai attack can have much higher fatalities per terrorist.)

The answer to this question is two-fold. First, the limits on the amounts of ammunition each terrorist carried. Second, the difficulties in actually inflicting fatal casualties.

First, let's ask how much ammunition each terrorist carried. Assuming that each terrorist carried eight hand grenades and a pistol, we can make the following approximate calculations:

Item Weight (grams)
Glock 17 Pistol 650
Two loaded pistol magazines 560
Eight hand grenades 2400
1 liter of water 1000
1 kg of food 1000
Cellphone, maps, cash, knife, etc. 500

Assuming that the terrorists each carried 22 kg — perhaps on the high side given the size of the bags the terrorists are shown wearing — then they could each carry an additional twenty-seven Kalashnikov (AK-47) magazines of 30 rounds each (576 grams each) for a total of 810 rounds of ammunition. While my numbers may be off, they do give us an idea of how many rounds each terrorist could expend: 810 from his assault rifle and 34 from his pistol.

It's hard to tell, but there doesn't seem to have been much in the way of pitched gun battles between the terrorists and the security forces; pitched battles could consume ammunition very rapidly while resulting in low casualties. Even so, one reason for the "low" casualty count is that the terrorists probably weren't carrying as much ammunition as one might expect — not thousands of rounds — and they probably reserved a good part of that ammunition for firefights with police and the military.

The next reason for the "low" fatality count is that in order to kill someone, you must arrange for your bullet to intersect with one of the victim's vital organs or to cause them to bleed to death. This isn't as easy as it may seem. After the 1973 Yom Kippur War, the Israeli Army determined that they expended 10,000 bullets per enemy fatality. As a result the Israeli Army changed their doctrine to require that all weapons be fired in single-shot mode and that all fire be aimed fire — no shooting from the hip.

The terrorists, however, did shoot from the hip. Furthermore, the hotels were not high-density kill zones: while many people may be present in a restaurant, the people are dispersed and fire towards one side of the room allows people at the other side time to move, evade, and escape; many did. After the initial attacks the terrorists did use their weapons as threats, which allowed the terrorists to force their victims to move into small hotel rooms with no exits — high-density kill zones. As for the railroad stations: again, despite firing into a potentially high-density kill zone, while a bullet may hit someone it does not necessarily create a fatal wound, and unaimed fire even at short ranges wastes ammunition. This, by the way, explains why the terrorists carried hand grenades; fragmentation grenades are very effective weapons which can kill any person standing within 4 to 10 meters and inflict casualties at much further distances.

Finally, a word about the response of the Indian forces to the attacks. Please remember that the terrorists hold a huge advantage: they want to inflict harm on innocent bystanders, and if the terrorists can arrange for civilian casualties to occur during a police or military rescue attempt, those casualties will create even further harm to the government — a win-win situation from the terrorists' perspective. The police and military face a tough problem: avoid casualties to their own forces; avoid casualties to innocent bystanders and hostages; neutralize the terrorists. These tasks have inherent contradictions, and a major incident such as this one strains the limit of the police and military to plan and execute a response.

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