The scourge of terrorism can't be stopped "unless some among us are willing to accept enormous sacrifice and risk to themselves," warned Prime Minister Stephen Harper.

He used the occasion of the fifth anniversary of the Sept. 11, 2001 terror attacks on the United States to remember the 24 Canadians who died that day, and to reinforce why Canadian soldiers are fighting in Afghanistan.

Harper said he remembered watching the second tower of New York's World Trade Center collapse on TV with his wife Laureen.

"As the enormity of the events began to sink in, I turned to her and said, 'this will change the course of history'," he said, according to remarks released in advance of his Monday night speech.

Since then, there have been bombings carried out in Bali, Indonesia, Madrid, Spain and London in Great Britain, to name a few, he said.

Many more plots have been foiled by security forces the world over, including Canada, he said.

"The targets and tactics were different in every case, but the objective is always the same: To kill, maim and terrify as many people as possible," Harper said.

"Not in the name of any idealistic cause, but because of an ideology of hatred."

• Full text of Harper's speech

While the war on terror has shown what humanity is capable of at its worst, Harper praised the goodness that flowed from ordinary people after the 9/11 attacks.

"Something which was on display for all to see when Canadians opened their arms and homes to thousands of travellers whose flights were diverted," he said.

Nations must confront the scourge of terror, Harper said.

And that is why the countries of the United Nations, with unprecedented unity and determination, launched their mission to Afghanistan," he said.

Operations to overthrow the Taliban -- which harboured the Islamist militant group al Qaeda, responsible for the 9/11 attacks -- began in October 2001.

Since the overthrowal of the Taliban, womens' rights have improved and children are going to school, he said.

"There are Canadian heroes being made every day in the desert and the mountains of southern Afghanistan. These are the stories that we don't hear -- the countless acts of courage and sacrifice that occur every day on the battlefield," he said.

"And in the towns and villages where Canadians are reconstructing the basic infrastructure of a shattered nation. Because of their efforts, the Taliban is on the run, not the charge."

Inside the House of Commons' Hall of Honour, Harper had families who had lost loved ones on 9/11 or who have loved ones serving in Afghanistan sitting behind him as he delivered his speech.

"Their presence here reminds us that real people -- Canadian men and women with families and children -- are courageously putting themselves forward to make that part of the world a better pace."

The prime minister asked Canadians to keep in their thoughts and prayers those whose loved ones perished on 9/11 and "the personnel and families of the extraordinary people in Afghanistan and elsewhere who have put themselves on the line so that the world is a better and safer place for all of us."

Analysis

In recent polls, Canadian support for the Afghanistan mission has been tepid. In a poll conducted between July 13-16 by The Strategic Counsel for CTV and The Globe and Mail, 39 per cent of respondents said they supported sending Canadian troops to Afghanistan versus 56 per cent who opposed the move.

CTV's chief political correspondent Craig Oliver told Newsnet the prime minister tried to emotionally link the events of 9/11 with current Canadian involvement in Afghanistan.

Oliver said the speech comes at a time when the Canadian mission in Afghanistan is in a bad patch.

"If you and I were in a street fight and we had to turn to onlookers and say, 'please give us help here', we wouldn't be said to be winning.

"And we've been forced to go to NATO and say, 'we are up against it here'," he said.

A year ago, the Taliban operated in hit-and-run raids. Now they are fighting in large groups, almost like conventional warfare, he said.

With the current talk of bringing in tanks, Oliver said military told him four years ago that tanks shouldn't be used because they separate our troops from Afghan population.

While Harper made an effective presentation, he didn't address many of the questions that should be asked about this mission, Oliver said.