Chief of the Defence Staff Gen. Jonathan Vance updated senators Monday on Canada’s evolving mission against ISIS in Iraq.

Here are 10 things we learned.

The number of Canadians deployed is increasing:

The government has said its redefined mission against ISIS will involve tripling the size of the military’s “train, advise and assist effort” on the ground, as well as increasing intelligence gathering and medical personnel.

That will require more troops. Vance said the military plans to increase the number of personnel deployed as part of Operation Impact to roughly 830, from approximately 650.

Vance said Canada has helped to ‘categorically stop’ ISIS from advancing:

Vance said the coalition managed to “categorically stop (ISIS)” from advancing on Baghdad and that ISIS has now been “pushed back, losing about 40 per cent of the territory they had taken over.”

“The degradation continues and we have played an active role,” he said.

“Canada’s part in this, I think, was tremendous,” he added. “We responded very quickly with the CF-18s as part of a coalition effort to stop this very rapidly advancing enemy.”

He said Canada contributed other things too, including “intelligence assets” and “a modest train, advise and assist mission with Iraqi Kurds.”

Vance stressed that a military mission alone can’t stop ISIS:

Vance said Canada’s military goal is to help Iraqi forces “degrade and ultimately defeat” ISIS, which will require “putting Iraqi forces back on the offensive” so they can help “re-establish the reach of governance.”

But he also said that a “political solution” is necessary to help deal with the “attractiveness” of ISIS “to the disenfranchised.”

Vance sees the conflict as dating back “millennia”:

“I think it’s well known and well understood that we are in the midst of a wider conflict, a conflict that has been going on for millennia, challenges that have been going on for a long time between the two major sects of the Islam faith, Shia and Sunni, and various proxy efforts that go on as a result,” Vance said.

The general also said he “can’t tell you it’s all clear how we will proceed,” but that the current mission aims “to deal with a clear and present massive destabilization,” and to avoid a “wider and faster destabilization.”

Vance said Canada is not “at war” with ISIS, but it’s complicated:

Asked whether Canada is “at war” with ISIS, Vance said the short answer is “no, Canada is not in a declared state of war.”

He said Canada is technically “a lawful party to an armed conflict against a non-state actor.”

At the same time, he said “it doesn’t necessarily matter” whether the word “war” is used, because it changes little about the mission for his troops.

The Kurdish forces being trained are mostly non-professionals:

“There are some elements of professionalized and partly-professionalized but they are almost exclusively civilians who need training on their small arms,” Vance said of the Kurdish Peshmerga Canada is working with.

“They need to understand how defensive battles are conducted, to protect themselves, and to use from a map and compass, all the way through to how to read your GPS,” he added.

Vance said Kurdish forces tend to show up for rotations, some of them three days long.

Vance was asked about how many Kurdish forces Canada is helping to advise, assist and train and he said he could not give an exact number.

“In the territory that we’re in right now, we’re in the range of 400 to 500,” he said, adding that territory is expected to expand.

“I think we want to improve that,” he added. “We want to make sure there are more and more people available.”

There are plans to give a “battalion size” group extra training:

Vance said a “battalion-sized” group of 300 to 400 could get extra training to turn them into “stronger core of more professional fighters (who) can reinforce the line if necessary or conduct offensive operations, potentially even in time to support the battle of Mosul.”

“We’re not building an army,” he said. “We’re building an effect that will last as long as it needs to last.”

The security forces being trained could help take back the major city of Mosul:

“The ultimate objective in the mid- to long-term will be the Iraqi security forces efforts to free Mosul,” Vance said. “Where we are deploying, we will be providing support for those who are working to contain (ISIS) in Mosul and ultimately lead to their defeat there.”

Vance said it’s “very difficult to put a timeline on it, but in 2016 or 2017, I would suggest to you, the battle for Mosul will start.”

Vance added that Mosul will be the “next significant battle and potentially last significant battle of this campaign.”

Gen. Vance added that the Mosul dam “will be in our vicinity” and there is “a question mark whether or not it will hold.”

Chemical weapons are a concern:

In response to a senator’s specific question, Vance said “reports that (ISIS) is in the possession of rudimentary mustard and chlorine chemicals and, again, rudimentary delivery means (are) accurate.”

He said that “it’s relatively small-scale, but I don’t take any solace in that,” adding that he’s also worried ISIS could get their hands on “nerve agents.”

Vance said the Canadian forces have “the best detection equipment in the world and great protection equipment,” plus intelligence gathering and drills in place that could prevent or mitigate the effects of chemical weapons on troops, although civilians wouldn't have the same protection.