Admittedly, the United States isn’t exactly on the BFF list for too many countries. Being the leader of the Free World may garner a certain measure of respect but not necessarily a lot of affection.

For two countries, however, the relationship with the USA goes well beyond diplomatic niceties. The United Kingdom has claimed a “special relationship” with the United States since the days of Winston Churchill and Franklin D. Roosevelt. Canada also lays claim to a unique level of friendship. The 5,525-mile (8,892-km) border between the two countries is the longest unguarded international border in the world, attesting to the high level of trust between the neighboring nations.

So why did the United States develop a top-secret plan to invade its neighbor to the north and to fight an aggressive trans-Atlantic war against its closest ally? The answer to this surprising question is found in War Plan Red.

The military is always at its best when it can focus its planning on an enemy. In the days following World War I (aka “The War to End All Wars”) it was a little difficult finding anyone who fell into that category. At least, it was hard finding any potential adversaries who posed a serious military threat.

Not wanting their planning skills to grow rusty, the Department of War (later renamed Department of Defense) focused its attention on a hypothetical military problem and tasked its officers with developing an appropriate plan.

The practice of planning against an unlikely scenario is not unique. As detailed in this article, the U.S. military has an impressive plan for safeguarding humanity in the event of the Zombie Apocalypse.

Widespread fear of zombies was still decades in the future in the years between the world wars, however. When military strategists turned their ever-keen minds on a worthy adversary, they chose the United Kingdom. Perhaps one or two of them still harbored a bit of a grudge over that little “it’s complicated” point in the nations’ relationship back in 1776.

An Army spokesman in 1928 admitted, “A war with Great Britain seems highly improbable in the near future.” It was useful, however, to think through the implications of that scenario. The British navy was the only force in the world capable of attacking both the continental United States and its dependencies in the Caribbean and the Pacific.

The result of this planning was “The Atlantic Strategic War Plan,” better known as “War Plan Red.” The nickname arose out of the use of colors to designate the different players in a multi-front war. As shown on a map, the United States was “Blue.” The United Kingdom and the nations that fell under the British Empire were “Red.”

War Plan Red was approved by Secretary of War Patrick J. Hurley and Secretary of the Navy Charles Francis Adams in 1930. It was updated in 1934 and 1935. The entire declassified plan is accessible here.

For planning purposes, it was assumed that the U.K. would be the ones picking a fight. Perhaps one or two of them still harbored a bit of a grudge over that whole Tea Party thingy. According to the strategists of War Plan Red, however, the more likely casus belli of hostilities would stem from “constantly increasing Blue (American) penetration and expansion into regions formerly dominated by Red trade, to such an extent as eventually to menace Red standards of living and to threaten economic ruin.” They concluded that the U.K. would be left with no other choice than to eliminate America as a commercial threat “by destruction of Blue merchant marine and foreign trade, and by acquisition of Blue overseas possessions, including control by Red of the Panama Canal.”

For planning purposes, the scenario assumed the Brits would focus their attack on the industrial centers in the north. To do this, they would send troops through the Montreal-Quebec region of Canada to “capture or destroy Blue vital war-making industries.” Ground attacks would be coupled with sustained bombing campaigns against “vital war industrial facilities and on centers of governmental, financial and industrial administration” in the cities of Washington, New York, and Pittsburgh.

At this time, Canada was still part of the British Empire, so it was assumed it would rally to the saber-rattling of the Crown. Its proximity to the United States put it in an ideal position to cripple the US war potential by seizing the Great Lakes waterways, thereby cutting off 90% of the U.S.’s iron ore transport.

While the U.S. was still trying to respond to the surprise Canadian hostilities, the British navy would be hard at work targeting American interests beyond the continental United States. The Panama Canal, American islands in the West Indies, and the Philippines would fall with the assistance of two other colonies of the Empire, Australia and New Zealand. By way of added incentive, War Plan Red assumed Canada would be offered Alaska, Australia would get some or all of the Philippines, and New Zealand would receive American Samoa.

British intelligence, it was assumed, would find easy allies in Mexico and Argentina who would pass along secrets and aid in the dissemination of propaganda. Although Mexico may not be in a position to attack the U.S., it could mass some troops along the Rio Grande, forcing the U.S. to tie down military resources to firm up the southern border.

The rapid success of Canada and the U.K. against the United States was not all that far-fetched. Although the U.S. had the world’s largest military at the end of World War I, it rapidly demobilized once fighting ceased. Consequently, America would be defending itself with a slightly smaller navy and much smaller army than its aggressors.

In the summer of 1930, the U.S. Army in the continental United States consisted of 102,700 officers and men. To provide the necessary manpower for the war, the National Guard militia of 175,000 would have to be mobilized, plus the Organized Reserve of 120,000. Even these numbers were insufficient, and planners confessed that the military would be severely curtailed by significant deficiencies in supplies and equipment.

Although outmatched militarily, the industrial strength of the U.S. would be its saving grace. It just required enough time to retool the industrial sector to prepare for war. War Plan Red proposed buying that time by launching a preemptive invasion of Canada (code-named Crimson). The full text of the plan to invade Canada can be read here.

Our readers in the vicinity of Halifax, Nova Scotia may be alarmed to learn that Ground Zero of America’s assault on the Canadian menace was to take place there. The plan called for an amphibious assault on the city, but if that did not work, Halifax was to be destroyed.

The 1934 revision to War Plan Red envisioned the immediate first use of poison gas, coupled with the strategic bombing of Halifax. Taking the city out of the picture would deny Great Britain a strategic port, severely limiting support to the Canadian military.

The state of Maine would function as a major center of operations for the USA military effort in those early days of the US/Canadian conflict. Military forces in Maine would be in a prime location to separate Quebec and Montreal from the Maritime Provinces and to provide a base for ground and airstrikes against Halifax and New Brunswick. It would also permit the United States to seize control of the Niagara Falls hydroelectric facilities, as well as cut off a strategic supply of Canadian coal to the U.K. and the western Canadian provinces. Successful occupation of this region would result in “an immediate strangulation of [Canada’s] manufacturing and munitioning capacity.”

The ultimate plan called for “the expulsion of Red from North and South America … and the definite elimination of Red as a strong competitor in foreign trade.” Getting Canada out of the way was a vital first step in these objectives.

Although War Plan Red was largely a hypothetical exercise, there were some real-world measures taken to prepare for a sudden deterioration in US/Canada relations. In February 1935, the War Department sought a Congressional appropriation of $57 million to build three border air bases to allow for pre-emptive surprise attacks on Canadian airfields.

General F.M. Andrews, testifying before the House Committee on Military Affairs, explained:

“It is not believed that Canada unless forced to do so would ever join a coalition against the United States, but if she were part of such a coalition, air force operations from a base in the Great Lakes area would be capable of dominating the industrial heart of Canada the Ontario Peninsula and prevent the establishment of enemy air bases in that area for operations against this particularly vital area here [indicating] which has been described. Air force units from the Great Lakes area could be transferred to the New England or Chesapeake areas in a matter of about 3 hours.”

February 11-13, 1935, hearings of the Committee on Military Affairs, House of Representatives, on Air Defense bases (H.R. 6621 and H.R. 4130), page 61.

This plan caused the United States a wee bit of embarrassment when the supposedly-secret testimony was published by mistake. The Canadian government protested strenuously, forcing President Franklin Roosevelt to personally assure his neighbor to the north that the USA was not preparing a hostile takeover of the country. It didn’t help that the New York Times ran the story on its front page on May 1, 1935.

Despite the bad publicity, the Wilcox Air Base Act was enacted on August 12, 1935, officially authorizing the Secretary of War to plan for hostilities with any hostile Canadian menace. That same month, the US held its largest peacetime military maneuvers to date. With 36,000 troops massing at the Canadian border south of Ottawa and another 15,000 held in reserve in Pennsylvania, Canadian authorities must have had at least a little anxiety that FDR’s assurances were unreliable.

Getting back to War Plan Red, the purpose of taking Canada out of the picture was to buy the U.S. enough time to ramp up its industrial might. Once that happened, the British navy would no longer rule the waves. The focus of military operations would turn to the seas at that point.

The U.S. Navy was to harass British traders in the China Sea and to cut off British trade routes in the Atlantic. This was no small thing for the island nation. Cut off from its supplies of wheat and nickel from Canada and meat from Argentina, the once-mighty British Empire would quickly fall to its knees.

The center of naval combat would likely be the Caribbean. The primary focus for the U.S. would be to safeguard the Panama Canal. This would be vital for keeping the east and west coasts of the U.S. well supplied and connected. It served the dual purpose of shutting off the flow of oil to Britain from Latin America.

Once fully battle ready, the U.S. Marines would take control of Jamaica, the Bahamas, Bermuda, Trinidad, St. Lucia and British Honduras. The Plan advised that “it is of the utmost advantage to cultivate a feeling of Pan-American solidarity” so there would be no resistance to the U.S.’s military objectives. If, however, the local governments proved to be less than fully cooperative, “Blue should be prepared to exert military and naval pressure against recalcitrant Nations of Central America and West Indies.”

The closing stages of the war presumed that Britain would surrender once all of Canada and the Caribbean were firmly under U.S. dominance. If not, the plan called for taking the war into the Mediterranean to further cut the U.K. off from supplies.

Actual British thinking about war with the United States at the time regarded Canada as indefensible and called for the use of Bermuda and Caribbean bases as jumping-off points for attacks on American commerce.

Fortunately, War Plan Red never had to be tested. In January 1938 Major-General Stanley Embick wrote that developments since 1933 had made the whole premise ridiculous. The growing German and Japanese menace gave the country actual enemies to prepare against. The U.S. Navy had all along taken the view that the real threat to America came from Japan and had seen planning for Red as a futile diversion. “From beginning to end,” wrote one senior naval planner in May 1939, “this plan has had little validity. It has not been supported and it was largely useless work.”

In 1939, on the outbreak of World War II, a decision was taken that no further planning was required but for the plan to be retained. War Plan Red was declassified in 1974.