KANDAHAR, Afghanistan - Canadian troops arriving at Kandahar Airfield are usually still jet-lagged when first introduced to the deadliest weapon they are likely to face the entire time they're in Afghanistan.

The constantly evolving threat of improvised explosive devices, the Taliban's weapon of choice, means new soldiers get a thorough and up-to-date briefing almost as soon as they get off the plane.

In recent months, the army's IED experts have noted a change in the design of the weapons. Older models often made use of such household items as pressure cookers and tin pots, scattering fragments of shrapnel over a broad area.

Newer models attempt to direct the blast in one direction in order to target specific elements of a patrol, they say. The Taliban's bomb makers have also been tinkering with the triggering devices to allow them more time to escape.

"As far as what they use for explosives, that remains the same," said Sgt. Charles "Chuck" Florian, a member of the army's counter-IED squad.

"It's how they ignite it, that's the advancements that they're making."

The gradual evolution of the Taliban's IED technology is a product of a major tactical shift in how they are fighting the insurgency. Whereas in the past the Taliban were content to openly confront Canadian troops, they have increasingly resorted to IED attacks.

Since April 2007, 63 of the 86 Canadian deaths in Afghanistan have been the result of improvised explosive devices. U.S. estimates figure that 75 per cent of its troop casualties are attributable to some form of IED.

"They love it (IED attacks)," Florian said of the Taliban. "The reason they love it so much is because there is no physical connection."

Army counter-IED experts, most of whom can't be named for fear of being individually targeted, monitor changes in bomb-making techniques across the region in anticipation that they may be used to target troops in Kandahar.

The more sophisticated materials for constructing IEDs are said to filter through Afghanistan's porous border with Pakistan and Iran. But triggering devices can be as simple as a toy clock, and the explosives as commonplace as ammonium nitrate-based fertilizer.

Though such fertilizers have been banned in Afghanistan for several years, Canadian troops are instituting a program to replace leftover stockpiles with a less volatile version.

Soldiers arriving in Kandahar spend an afternoon getting acquainted with the latest IED technology as well as the equipment and methods outgoing troops have developed to defend themselves.

Though most received IED training before leaving Canada, they are quickly told that some of what they learned simply cannot be applied in Kandahar, especially amid the unpredictable alleys of Kandahar city.

"Make sure you understand the insurgents you're fighting are really smart," they are told.

They are brought up to speed in a corner of the expansive ISAF base at Kandahar Airfield that has been turned into a veritable IED school, complete with blackboards and teaching aids.

But the margin of error is decidedly smaller than your average classroom. Ignore the lessons, they are warned, "and you either kill yourself or kill your buddy."

Cpl. Caroline Livesey hadn't been in Afghanistan more than 12 hours before her unit was dispatched to Florian and his fellow instructors.

"It's a good refresher and a good swift kick in the butt," she said.

"Knowledge is power out here."

The new arrivals are shown a variety of different IEDs and the different methods insurgents use to set them off. They are trained how to look for certain indicators that may tip them off about the location of hidden explosives.

Their attention is also directed towards the sinister creativity insurgents display in creating vehicle-born IEDs, such as turning bicycles into suicide bombs. One jeep on display had a detonator jerry-rigged to its bumper, set to explode when it rammed into a convoy.

"It really brings it home," said Master Cpl. Chris Wood, still bleary-eyed from the flight over. "You really snap to."