The Secret U.S. WWI Plan to Invade Canada
Few Americans realize that in the 1920s, the U.S. military secretly prepared for war against Canada.
In the years following World War I, as Europe struggled with political upheaval and new alliances, the U.S. military quietly drew up plans for scenarios few would imagine today. One of the most unusual was “War Plan Red,” a detailed strategy for a hypothetical conflict with the British Empire. Among its most surprising components was an extensive, secret plan for the invasion of Canada.
War Plan Red was part of a series of “color-coded” war plans developed by the United States Army and Navy between the 1900s and 1930s, each addressing possible conflicts with different countries. “Red” was the color assigned to Britain, while “Crimson” referred to its northern dominion, Canada. The plan reached its height of development in 1930, influenced by theoretical concerns that British global power—though weakened by the First World War—remained a potential threat to American interests, especially as the British Empire controlled vast territories and high-seas naval routes.
The plan’s rationale was based less on probable events and more on strategic prudence: American military planners believed in being prepared for any contingency, however unlikely. Anglo-American relations had not always been friendly—earlier in the 19th century, the two nations had fought the War of 1812, and mutual suspicion lingered. The rise of Japan and the collapse of the old European order meant the U.S. wanted to consider every possibility.
War Plan Red detailed not only theoretical warfare on the high seas but, more shockingly, an actual land invasion of Canada as a first strike, designed to preempt a British attack and secure the northern border. According to declassified documents, the U.S. military proposed striking key points: Montreal and Quebec would be captured to cut off vital rail links; the Great Lakes region would see coordinated assaults from multiple fronts; and major Canadian cities such as Halifax and Vancouver would be targeted to prevent British reinforcements from using Canada as a staging ground.
To enable surprise, the plan recommended quickly seizing strategic railway hubs and bridges in Canada. In order to secure New England, U.S. forces were to occupy parts of the Maritimes, including Halifax, a vital naval port. Strikingly detailed logistics included estimates for troop numbers, supply needs, and even the use of chemical weapons, which were permitted under the conventions of warfare at the time.
Canadian officials were aware of the possibility that their territory might be used in any Anglo-American conflict. In fact, Canadian military planners worked on their own versions of a counter-invasion, developing “Defence Scheme No. 1,” which called for lightning attacks on several U.S. border cities—such as Seattle, Fargo, and Albany—in order to delay an American advance long enough for British reinforcements to arrive. Canadian officers even conducted clandestine reconnaissance missions within U.S. territory, mapping roads and bridges they might need to use.
Despite the level of detail and earnest effort, these war plans were never acted upon. The rising threat of Nazi Germany and Japan in the 1930s and early 1940s rapidly made Anglo-American cooperation not only likely, but vital. War Plan Red was quietly shelved and eventually declassified in the 1970s. Today, these schematics are a reminder of a time when the world was unpredictable and military planners, charged to be ready for anything, saw even the friendliest nation as a possible threat.
While War Plan Red may sound almost comical in hindsight, it represents the seriousness with which early 20th-century militaries approached the unknown. Few Americans realize that their country once earmarked the route to Montreal or plotted the occupation of Nova Scotia, and fewer still have heard of the long-forgotten schemes shared across the U.S.-Canada border—a testament to how much international friendships can shift with the currents of history.
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