I'm the last guy to be an "America-wanker", but I'd like to shoot down two things that get a complete waive every time this is mentioned:
1. Defense Plan 1 seriously impeding the United States.
Define "seriously impede". The purpose of DP1 wasn't to knock the US out of the war, but to cause enough chaos (by ripping up railway lines, blowing up bridges, stealing locomotives, etc.) to delay the American invasion by long enough to allow Britain to ship reinforcements across the Atlantic. Even if it only took a week or two for the Americans to drive out the invaders and bring up enough replacement infrastructure to start their own invasion then DP1 will probably have succeeded.
It's a quixotic effort at best, and what it sounds like in reality is wasting Canada's already meager defensive power in an offensive of questionable utility...you can destroy a couple of bridges and factories, for sure, but I'm not seeing occupying Albany and Buffalo for 24 hours as really achieving much.
"meager defensive power". Time for some numbers perhaps. Joint Plan Red assumes the following forces available in CONUS at the start of mobilisation (M-day):
Regular army - 100,000 men in 9 divisional organisations
National Guard - 175,000 men in 18 divisional organisations
Organised reserve - 118,000 men (of whom 113,000 are officers). The purpose of this formation is to fill out the two bodies above to full war strength and act as cadre for another 33 divisions of fresh conscripts rather than to fight directly.
Note that according to the plan available forces could be moved up to the border by M+4 but they wouldn't be fully mobilised and ready to go until M+60.
On the other side of the border, War Plan Red assumes the following numbers:
Canadian army 52,000
Canadian reserves available after 30 days 68,000 (120,000 in total in 11 divisions)
British expeditionary force available in theatre after 30 days 100,000 (4 infantry divsions and 2 cavalry brigades).
Other Dominions and India - no details here, but War Plan Red estimates total Imperial forces in Canada after 60 days could be 270,000 men (note this is not significantly less than the combined total of US Army/National Guard).
The critical factor here is how soon after M-Day the penny drops and Britain and Canada start mobilising in response. If it's very quick and the flying columns head over the border before the Americans have properly moved up and secured it, then going by the above figures by the time the US are ready to launch an invasion the invaders will be matched in numbers by the Imperial forces in Canada - hardly a recipe for a successful invasion, never mind a swift one. And things get worse after that - with full Imperial mobilisation and ability to reinforce North America (i.e. the worst case scenario for the US) War Plan Red assumes 460,000 Imperial troops ("Some of the colored races however come of good fighting stock, and, under white leadership, can be made into very efficient troops" - presumably a reference to the Indian Army...) in North America after 6 months, 1 million in 9 months and 2.5 million in 77 divisions after 16 months. to be fair, on the other side of the coin Red assumes 2.1 million American troops by M+120 and 4.6 million after two years, but as these figures are dependent on a conscription law coming into effect by M+60 the vast majority of these (especially the M+120 numbers) will be untrained conscripts.
Of course, and to repeat, all of this depends on the RN being able to establish control of the Atlantic (or at least prevent the USN establishing control). If it doesn't, then all bets are off. FWIW, Red seems to assume that the first actual combat operations would involve a British attempt to close the Panama Canal in response to American moves to shift their Pacific fleet into the Atlantic.
I'm not saying that Canada won't put up a valiant effort. I'm just saying that the United States will "win", and soon.
See above. War Plan Red is assuming a total war lasting at least two years. I'm not sure if that fits your definition of soon, but...
Note on sources - all the above is drawn from the excellent article in the Autumn 1988 edition of Military History Quarterly magazine. This is offline as far as I can see, but there is another nice article in the Washington Post
here. Favorite quote - "Invading Canada is an old American tradition. Invading Canada successfully is not. "
