After several months of preparation by an advance team, the first Canadian infantry -- whose job it will be to patrol the streets of Kabul -- have arrived in Afghanistan.

More than 100 soldiers landed in two Hercules aircraft early Friday. They've arrived to replace German and Dutch troops that have been operating as part of the 25-country international security assistance force (ISAF) since last year.

Canadian task force commander Maj. Gen. Andrew Leslie says this mission will be more complex and volatile than anything Canadian soldiers have ever seen.

"We've suffered a significant number of soldiers killed and injured in other parts of the world, but I think this is perhaps the first time we've actually encountered the degree of fanaticism which is out there on the streets of Kabul," Leslie told CTV News.

But Leslie says his troops will not hide from danger, as he believes the most effective means of operating in Kabul is to have some troops patrol on foot.

"The more soldiers you have out vulnerable and exposed with boots on the ground the higher the potential risk," Leslie said.

"Having said that, we have a job to do. ... You can't get to know them if you roar by them in 15-tonne vehicles going 30 kilometres an hour."

For Lt.-Col. Helmut Remus, commander of the outgoing German battle group Canada's soldiers will be replacing, being exposed on the street poses a distinct challenge.

"Not all Afghanis know what Canada is,'' Remus told Canadian Press. "They think you are Americans. This could cause problems."

"It is very important for the Canadians to show the flag -- the Maple Leaf. Some Afghanis are not happy about the Americans here. It is important to make it clear that Canada is not America.''

In fact, the nearest American presence is about 40 minutes' drive away in Bagram where, along with troops in the southern city of Kandahar, the United States is still waging war on elements of al Qaeda and Taliban.

Those same threats, plus rogue warlords, weigh heavily on the minds of commanders and troops in Afghanistan, Remus said.

Not to mention the daily threats of rocket and suicide bomb attacks.

"Everybody in ISAF should expect casualties," said Remus. "You have to deal with this. You have to be friendly and work with the Afghanis.

"But at your back, you feel the threat every minute. We know our enemies, but we don't see them. This is a really hard mission."

In a little over a year of active duty in Afghanistan, Remus's contingent has suffered 52 casualties, including four killed and 29 wounded in the suicide bombing of a busload of German troops this spring.

Canadian troops have already taken some steps to distinguish themselves from other international forces, including opting for green combat fatigues over the desert browns worn by Germans, Australians, Britons and Americans.

Next week, the Canadian troops will start patrolling Kabul's streets alongside their European counterparts.

And starting August 21, they'll be on their own.

Based on reports by CTV's Matt McClure and The Canadian Press