Why an American move against Canada would be difficult

Canada would need time to retrain and equip forces intended for Pacific service, and orders placed with North American factories would not arrive immediately. That delay would not make a spring invasion easy for the United States. Canadian forces would have mobilized for several months, while the U.S. Army would still be expanding from a low peacetime base. Halifax and other ports identified in War Plan Red would have alerted garrisons. A thrust at Vancouver is more geographically plausible than one against Halifax, but it pulls naval strength away from the Pacific.