Monday, July 11, 2005

Post-Attack Assessment: How?

Brit Police and Security services are releasing little information - a shame because it's likely that the terrorist cell is still active. We need to know how they operate so we can defend ourselves, so here's my informed guess. It suggests we can expect more attacks.


10 to 20 pound shaped plastic explosive charge, with commercial detonators triggered by digital timers. Shaped charges focus the force of the explosion in a particular direction, and the bus that was damaged shows that the energy mostly went sideways and upward. That gets maximimum caualties from a bomb placed at floor level.

The timers probably has minimum and maximum delays, anti-handling triggers designed to kill security personnel, IRA-style, and possibly manual shutoffs.

With enough money, the explosive and detonator are easy to source and build, but the timing mechanism needs to be reliable and carefully assembled and tested. Also charge-shaping is a specialist task. So an expert bomb-maker was involved. He may have misled the bomb carriers about the weapon's triggers - witness the captive Palestinian woman who tried to blow up the Israeli hospital trying to trigger her bomb, without success. It probably had a "not before" override to protect the bomb-maker.

Bombs of this size are easily hidden in a case or backpack - the Palestinian had 20 pounds strapped around her waist, under a traditional robe.

Deployment - Underground Train

The Underground bombs were all reported as next to carriage doors. This suggests the bombers boarded the train, placed backpacks by the doors, then jumped out just as the the doors closed - you can do this by blocking the doors as they close, which causes them to re-open briefly. You need something solid to block them though, they close with great force. The passengers were doomed at that point, because once the doors are shut, they cannot be reopened. Pulling the emergency handle at best just stops the train.

I don't think these were suicide bombers - for maximum casualties, these would have positioned themselves in the center of the carriages and away from the doors. And suicide bombers would not have needed shaped charges - they're trained to stand up before detonating, to maximize de-limbing of victims - this mutilation is invariably fatal.

The bombers would have been smartly dressed and clean shaven to minimize suspicion. They would have worn heavy shoes to ensure that they could stop the doors closing.

Deployment - Bus

This looks like operator error - the bomber was on the upper deck, whereas for maximum casualties he needed to be downstairs. The bus was full of passengers evacuated from a closed Underground station & there was likely no room downstairs. In which case the bomber needed to get to another bus with more room. It's possible that he triggered the anti-handling while trying to delay the timer. Ot the bomb maker might have built in an "explode by latest time", or wired a "make safe" control to detonate the bomb. All of these of course without telling the bomb carrier. There are (unreliable) witness reports of a man frantically fiddling with the contents of his backpack.


The specialist bomb-maker came from outside the UK and remained until the bombs exploded. The IRA works for hire so could have supplied the man. More likley he's Arab - UK immigration control is poor, so he'll have little difficulty coming and going with Syrian- or Iranian-supplied passports. He'll be hidden in London's large Muslim community.

The bomb carriers were probably Al Queda trained Muslim Brits - planting the bombs would be easy, just requiring the right psychotic mindset. The IRA has about 300 people prepared to commit mass murder, out of a Catholic population similar in size to the Brit Muslim community. The IRA also has about 30,000 people ready to provide them shelter and support, and Islamic bombers will likely have the same.


If the bomb-maker is still here, they'll attack again. To avoid the extra surveillance on busses and Underground, they'll go for other soft targets, of which there are plenty - for obvious reasons, I won't list them.

The good news is that, knowing how they work, we can counter them. I'll post on that next.