Taking Canadian cities would not end the land campaign because occupation forces could face a morale-sapping guerrilla war across terrain rich in concealment and supply routes. Britain could continue feeding that resistance with resources from outside. American War Plan Red is treated largely as a staff exercise, while Canadian planners prepared for the one plausible invasion threat on their border. Those planners gathered practical local knowledge and might attempt rapid moves against border cities before the United States Army fully mobilized.
Notable Point · 2:24:33-2:25:10
Why occupying Canada would not settle War Plan Red
American occupation could face sustained Canadian resistance, British resupply, and a defence plan developed with more practical attention than Washington's staff exercise.