But both the Opposition New Democrats and the Liberals balked, citing the last 10 years of Canadian experience in similar such conflicts as their rationale for why this time, we should stay out of the fight.
Canada will spend up to six months participating in the U.S-led airstrike campaign in Iraq, Harper said. Dropping bombs in Syria remains a possibility, he added, but no Canadian soldiers will take part in ground combat.
The 69 special-forces "advisers" already committed to the fight against the militant group known as the Islamic State of Iraq and the Levant would remain part of the operation for the same time frame, Harper said.
Their initial 30-day mission window was scheduled to close Saturday.
"ISIL has established a self-proclaimed caliphate, at present stretching over a vast territory roughly from Aleppo to near Baghdad, from which it intends to launch a terrorist jihad not merely against the region, but on a global basis," Harper told the House.
"Indeed, it has specifically targeted Canada and Canadians, urging supporters to attack 'disbelieving Canadians in any manner,' vowing that we should not feel secure even in our homes."
Despite the weighty subject matter, Harper spoke to a Commons that was only half-full — not an uncommon occurrence for a Friday.
He said Canada would dispatch one air-to-air refuelling aircraft, two Aurora surveillance planes and all the necessary air crews and support personnel. Oddly, he neglected to mention Canada's CF-18 fighter-bombers. Up to six will take part, a spokesman later confirmed.
The U.S., France, the United Kingdom and Australia are among those countries currently taking part in airstrikes in Iraq, the latter country having just green-lighted its own participation on Friday.
That news came on the same day that a new Internet video was released purporting to show an ISIL fighter beheading British hostage Alan Henning — the fourth such killing by the group — and threatening yet another American captive.
The video mirrored other beheading videos shot by ISIL, which now holds territory along the border of Syria and Iraq. It ended with an Islamic State fighter threatening a man they identified as an American.
"Obama, you have started your aerial bombardment of (Syria), which keeps on striking our people, so it is only right that we continue to strike the neck of your people," the masked militant said.
Harper said the intention of Canada's mission in Iraq isn't to eliminate ISIL, but rather to reduce the territory in which the al-Qaida splinter group currently operates.
"We intend to significant degrade the capabilities of ISIL, specifically its ability either to engage in military moves of scale or to operate bases in the open."
Neither the Opposition NDP nor the Liberals were sufficiently moved to provide their support, saying they'll vote against the motion Monday. The vote is largely a formality, since the Conservatives currently hold a majority of the seats.
Harper has simply left too many questions unanswered, said NDP Leader Tom Mulcair.
"The prime minister insists that this mission in Iraq will not be allowed to become a quagmire, but is that not precisely what our American allies have been facing in Iraq for the last 10 years," he said.
"Will Canada be stuck a decade from now mired in a war we wisely avoided entering a decade ago?"
The strife in the Middle East has been happening for generations and won't end with another war in the region, he said.
"It will end by helping the people of Iraq and Syria to build the political, institutional and security capabilities they need to oppose these threats themselves," he said. "Canada, for our part, should not rush into this war."
Trudeau said the ghosts of the last war in Iraq — a war he said was sold to the public on false pretences — haunt this one too.
"We cannot make the wrong decision now because the wrong decision was made then."
Harper has gone to the Commons seeking support for a combat mission before — to expand Canada's role in the NATO-led mission in Afghanistan and to join NATO-led efforts against Moammar Gadhafi in Libya.
A key difference this time around is that the mission command isn't as clearly defined, said retired colonel George Petrolekas, a former strategic adviser to Canada's top defence chiefs.
"Who is commanding? Are there any limitations to the kind of targeting we might do and who approves it from a Canadian standpoint or do we just take the targeting list?
"That would be a worthwhile thing to know."
— With files from The Associated Press
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Here is a copy of the motion:
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