Canadian soldiers in Afghanistan face a season of heavy fighting against the Taliban this spring, two security experts say, a fact that was made clear after two separate IED attacks killed four Canadian soldiers on Friday.

The four fallen soldiers -- identified as Master Cpl. Scott Vernelli, 28, Cpl. Tyler Crooks, 24, Trooper Jack Bouthillier, 20, and Trooper Corey Joseph Hayes, 22 -- were killed during an operation to disrupt Taliban command centres and supply lines.

Such operations are deemed necessary to cripple insurgent activity, particularly in the south where Canadian troops are stationed, and spring marks the time of year when that activity increases, says security expert Alan Bell.

Supply lines re-open after the cold winter and insurgents begin moving freely again through the country, and they have to plant IEDs and other roadside bombs to take on coalition troops.

They will also likely step up attacks against coalition soldiers once the addition 17,000 U.S. troops arrive in the country, Bell said.

"The Taliban stated ... that this was good from their perspective because they now have more targets to attack," Bell said Saturday morning on CTV Newsnet. "So despite the fact there's going to be 17,000 or 18,000 additional U.S. soldiers placed into the Kandahar region, once again the Taliban will be looking at all means at their disposal, which includes the use of IEDs, to prevent (coalition soldiers) from moving inside their battle space."

Walter Dorn, a professor at the Canadian Forces College, said a "very bloody" winter has foreshadowed what looks to be an equally dangerous spring in Afghanistan.

"We know that the drug trade is prospering and that the Pakistani problem is only getting worse," Dorn told CTV Newsnet on Saturday morning.

"So, we predict that the spring offensive will be very bloody and it will require a huge amount of effort to protect ourselves and our troops, as well as to be able to do something deeper, which is trying to win the hearts and minds of the local population so that the Taliban and the other insurgents don't get the kind of support that they need in order to carry out their attacks."

Vernelli and Crooks died in an early morning blast at about 6:45 a.m. local time while on foot patrol in the Zhari district west of Kandahar. Another five Canadian soldiers were injured in that attack and a local interpreter was killed.

Bouthillier and Hayes were killed about two hours later when their vehicle was struck by a roadside bomb attack in the Shah Wali Kot district, about 20 kilometres northeast of Kandahar city. Three others were injured.

All of the soldiers were based out of CFB Petawawa.

The offensive, called Operation Jaley, was a joint effort by about 2,000 Canadian and U.S. troops, the largest Canadian-American military operation since the Korean War.

The commander of Canadian troops in Kandahar, Brig.-Gen. Jonathan Vance, said Saturday that such operations are necessary to try to delay, rather than eliminate entirely, a heavy season of fighting.

Vance said the soldiers' work likely delayed Taliban operations by a month. During the operation, soldiers recovered enough material to make between 30 and 50 IEDs, CTV's Jennifer Madigan reported Saturday from Afghanistan.

The soldiers also recovered a number of weapons and took 15 detainees, Madigan said.

It is also important to hamper the insurgents' ability to disrupt the upcoming presidential election, which is scheduled for Aug. 20, Vance said.

It is yet unclear if a planned influx of about 17,000 American soldiers will help or hinder the security situation in Afghanistan.

The increased presence of U.S. troops in the country should help coalition forces crack down more heavily on Taliban activity, but it may also boost insurgent attacks on foreign troops.

The soldiers' deaths bring the total number of Canadian soldiers killed in Afghanistan to 116.

With files from The Canadian Press