How Would a US Canadian War Play Out?

The update of Canada's Defence Scheme No. 1 is a war plan for Canada in the increasingly credible likelihood of a conflict with the United States. 

A major portion is a surprise invasion of the northern United States as soon as possible after evidence was received of a US invasion of Canada. It assumed that the US would first attempt to capture Montreal and Ottawa and then Hamilton, Toronto, and Vancouver and the rest of British Columbia. Updates to Defence Scheme No. 1's are parallel to updates of the Pentagon's War Plan Red (see it here), a plan to invade Canada.

The purpose of invading the US is to allow time for Canada to prepare its war effort and to receive aid from Britain. According to the plan, Canadian battalions in western Canada would immediately be sent to seize Seattle, Spokane, and Portland. Canadian troops would also attack Fargo and Great Falls, then advance towards Minneapolis. Troops from Quebec would be sent to seize Albany in a surprise counterattack while troops from the Maritime Provinces would invade Maine. As US resistance grows, the Canadian soldiers would retreat to their own borders, destroying bridges and railways to delay US military pursuit.

Some see the Canadian plan as "suicidal" particularly if the US launched a nuclear strike. There also may be no British plans (yet) to send a large army to support Canada.  

Nuclear Weapons Supporting Canada

The use of UK and French SLBMs against the US is unlikely even if there is a Russian-US (RUS) military alliance commanded by joint US-Russian President Putin.

A crucial Canadian base that could host smaller nuclear weapons (more viable to use) is in Greater Halifax, Nova Scotia. That is Shearwater Nuclear Submarine Base. That base is known to host French, US and UK SSNs. Time will tell whether US-Canadian defence relations get so bad US subs cease coming to Shearwater or Canada bans them from Shearwater.

In times past French and UK SSNs and conventional subs had nuclear warheads on some torpedoes. France has long had air launched missiles with nuclear warheads. The warheads could be reconfigured for submarine launched anti-ship and MdCN land attack missiles. These could be sold to the UK or the UK could dust off designs for miniaturisation and modernisation as SSN weapons.  Another nuclear warhead platform could be the Tomahawk missiles already on UK SSNs. 

Canada's best strategy in the medium-long term would be to engage in a defensive war against the US, while seeking international political assistance against Russian directed US aggression.