In Afghanistan, the most important Taliban allies are smugglers and corrupt officials. That's because the hundreds of IEDs (Improvised Explosive Device, a roadside, or suicide car bomb) manufactured each week, depend on smugglers to get the essential ingredients (ammonium nitrate and aluminum powder) into the country. Both these items are forbidden in Afghanistan, and have to be smuggled in. Despite increased vigilance on the border, NATO troops have found that too many Afghan police or soldiers can be bribed by the smugglers, letting truckloads of this stuff into the country.
IEDs now cause over 50 percent of NATO casualties. It has also been discovered that there was one big difference between the IEDs in Iraq and Afghanistan; the explosives used. In Iraq, there were thousands of tons of munitions and explosives scattered around the country after the 2003 invasion was over. This was the legacy of Saddam Hussein, and the billions he spent on weapons during his three decades in power. The Iraqi terrorists grabbed a lot of these munitions, and used them for a five year bombing campaign. The Taliban face a very different situation.
With no such abundance of leftover munitions, the Taliban had to fall back on a common local explosive; ammonium nitrate. This is a powdered fertilizer that, when mixed with diesel or fuel oil, produces a semi-liquid slurry can be exploded with a detonator. While only about 40 percent the power of the same weight of TNT, these fertilizer bombs are effective as roadside bombs. But they are bulkier as well. Moreover, the fuel oil must be mixed thoroughly and in exactly the right proportion, otherwise the explosive effect is much less than expected. But the biggest problem is that if you can't get the ammonium nitrate, you have no explosives. So, U.S. and NATO forces are now on the search for ammonium nitrate. Even the supplies held by farmers are being taken, although the troops are paying twice what the farmers paid for it. Thus many farmers are voluntarily turning their ammonium nitrate (usually in 50 kg/110 pound bags) in for the instant profit. Other, non-explosive, fertilizers are made available to the farmers, at equivalent cost to ammonium nitrate. Legal imports of ammonium nitrate into Afghanistan are monitored. All this doesn't make it impossible for the terrorists to get the stuff, but it is more difficult. This was supposed to result in fewer, and less powerful, bombs. Didn't work out that way. Smugglers recognized an opportunity when they saw one. This was especially true with an additive that made ammonium nitrate bombs even more powerful.
Aluminum powder, when added to the slurry, makes the explosive go off faster, creating a more destructive shock wave (of compressed air). The aluminum powder must be added to the slurry in the right proportion, but a little of it, in the right proportion, will make a bomb much deadlier. Aluminum powder is forbidden as well in Afghanistan.
But as long as the Taliban have the cash to pay the bribes and the smugglers, the bomb ingredients will keep getting through.