MPs are expected to vote Monday on the Conservative government's decision to join allies in airstrikes against the extremist Islamic State of Iraq and the Levant (ISIL), which has been terrorizing stretches of Iraq and Syria.
The opposition NDP and Liberals have indicated they will not support Prime Minister Stephen Harper's plan, partly out of concern Canada could be dragged into a lengthy quagmire. The government's majority is expected to ensure swift passage of the motion following debate in the Commons.
In an interview with CTV's Question Period broadcast Sunday, Nicholson stressed the motion before Parliament would commit Canada's CF-18 fighters for a maximum of six months.
But he stopped short of promising that would be the end of Canada's combat mission.
"What we're asking for right now is up to six months, and we've been very clear on that," Nicholson said, adding, "we always have to assess what we're doing."
The New Democrats and Liberals have proposed a bigger humanitarian role for Canada to help refugees fleeing the bloody strife that has beset the region.
NDP Leader Tom Mulcair predicted Harper would return to Parliament in six months seeking to extend the military mission. Muclair pointed to the turmoil unleashed by the U.S.-led invasion of Iraq in 2003.
"If the Americans couldn't get the job done in a decade, we're not going to get it done in six months," he told CTV. "We have to learn the lessons of the past."
In his statement Friday outlining Canada's plan, Harper insisted the government is "seized with the necessity" of avoiding prolonged hostilities. "Indeed, we and our allies are acting now precisely to avoid a situation that was clearly headed to a wider, protracted and much more dangerous conflict."
Canada would join the United States, Britain, France, Australia and others in airstrikes intended to stop ISIL from engaging in large-scale military movements or operating bases in the open.
There is no way to destroy ISIL from the air, said Roland Paris, director of the Centre for International Policy Studies at the University of Ottawa.
ISIL forces have adapted to the threat of western air power, dispersing and hiding in populated areas, which will diminish effectiveness of aerial bombing raids, Paris said Sunday in an interview.
Within six months ISIL could collapse or its forces could advance, he said.
"But the odds are that they'll stay entrenched where they are until somebody tries to force them out. And the indications are there is no ground force that has yet been constituted to do that."
That key factor could pose a dilemma for Harper, Paris added. "I think that once you commit military forces to a combat mission, it can be politically difficult to remove them. So in practice it's a significant decision to make the initial commitment.
"I don't really understand the rush for the combat decision today when even a few weeks from now we would probably know a lot more about the viability of the larger strategy."
The group Homes Not Bombs plans a peace vigil on Parliament Hill while MPs debate the government motion to go to war.
ISIL is in the business of mutilation, rape and murders, and Canada must take action, Nicholson said.
"This terrorist group has fulfilled all the threats that they have made in the past, and so needless to say I and everyone in the government is very concerned about a direct threat to this country."
Nicholson did not provide an estimated cost of the combat mission, saying some of the money would come out of existing budgets. "But there will be incremental costs, and we will watch that over the next number of months, and we'll be very transparent and open about what those costs will be."
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