Historically, the United States has planned to go to war with just about everyone. There’s a good chance that a filing cabinet somewhere in the Pentagon has a folder labeled “Kingdom of Tonga” or “Peru.” Here are a few of the more bizarre plans, from history and today.
1. New Zealand
In 1908, the United States sent 16 warships to New Zealand. The Kiwis, harboring no ill will toward the United States, welcomed the "Great White Fleet" with open arms. After all, it was good to have a counterweight to the region's burgeoning Japanese military presence. Should war erupt, New Zealanders thought, the U.S. could help restore order to the region.
In reality, however, the U.S. warships were there on a reconnaissance mission. Were a war to break out with Japan, President Teddy Roosevelt feared that England would side with Japan, because of the Anglo-Japanese Alliance of 1902. And where went England, so went Australia and New Zealand. Accordingly, the U.S. fleet was actually in town to plan an invasion of New Zealand. Fortresses along the north shore were analyzed for tactical value, size, and armaments. U.S. military officials wrote back to Washington, "Any of them could probably be occupied with little or no opposition provided the attack was sudden." Newly-conquered Auckland would make a fine U.S. base of operations in the region.
In the decades preceding World War II, the United States organized its military strategies by color. To name only a few: The British Empire was Red; China was Orange; Mexico was Green; and in every scenario, the U.S. was Blue. By 1939, it was clear that in an increasingly complex world, no military campaign would ever pit just two colors against each other, and a new set of war plans were conceived: the Rainbow plans. Those scenarios involved complex alliances and conflict on multiple fronts. The plans were categorized as Rainbow 1 through 5. That's how the novel Rainbow Six, by Tom Clancy, was named. ("Six” can also refer to the commanding officer of a unit; the “six” of Rainbow was John Clark.)
Before the Rainbow era, however, War Plan Green assumed the general collapse of the Mexican government, replaced by a much worse outlaw government. Amidst revolutionary lawlessness, the United States would step in, protect its assets, and establish order. (Relations weren’t particularly friendly at the time, and during the 1910s, the U.S. actually did mount military incursions on Mexican soil.) War Plan Green involved the U.S. Army and Navy waging full-scale war on the Mexican coasts and along our shared border. The Army would thrust deep into Mexico, seizing cities and suppressing guerilla fighters. The goal would be the installation of a government friendly to the United States.
Early into World War II, military officials from the United States grew concerned about a remote chain of islands to the west of Europe. Called the Azores, they belonged to Portugal and posed a thorny problem. Though Portugal remained neutral (they were too fascist for the Allies, but not quite willing to throw in with the Axis Powers), there was a fear that if Hitler decided to invade Portugal, he would probably win, and the Azores would then belong to Germany. Once under control of the Nazis, the Azores would form a western front of sorts against Great Britain, and wreak havoc on trade.
To prevent this, the United States drew up plans to mount a sneak attack on the Portuguese Azores. We would invade and occupy the island, keeping Hitler out. It was a good plan as far as surprise attacks go, but there were two problems: one, we hadn’t yet entered World War II, and two, Portugal was not interested in dealing with an American presence. It's hard to imagine a messier entrance into the war. Still, it almost happened; the U.S. drew up formal plans and began training soldiers and Marines for the invasion. In the end, however, Hitler decided to invade the Soviet Union, leaving Spain and Portugal alone. War Plan Gray, as it was called, was thus abandoned.
War Plan Red was a 1927 invasion plan in which the United States would invade parts of the British Empire. Why would we do such a thing? One, because of the Anglo-Japanese Alliance of 1902 (which also led to our plans for invading New Zealand); and two, because there was lingering resentment by Washington D.C. of England's slightly-too-chummy relationship with the Confederacy during the Civil War.
War Plan Red involved defending the east coast of the United States while simultaneously going after the British Empire—specifically, Canada. (While invading Canada seemed perfectly sane, invading the British Isles would have been madness.) The American plan was simple: Destroy Canada's airfields in a surprise attack, and roll on in. Meanwhile, we would starve the British by way of a blockade, leading ultimately to a surrender. We would not give Canada back. In fact, ideally, we would soon begin slicing up newly-annexed Canada and organizing the regions as new states of the U.S.
Bonus: The Canadians Strike Back!
Defense Scheme No. 1 was a planned Canadian counterattack against the United States. See, it's not like America's Hat was sitting up there doing nothing. They knew that a sneak attack could come at any moment and they wanted to be ready. (In fact, DS1 was written before War Plan Red.) The plan worked like this: At the first hint of an American invasion of Canada, Canadian armies would begin an invasion of their own. Canadian soldiers would be sent in as that country’s air forces bombed Washington state, Oregon, Maine, Minnesota, and New York into submission.
This was a real plan. Canadian officers did field reconnaissance and everything, even sizing up whether American sympathizers might rise up and join the Canadians. In the event of a defeat, Canadian forces would destroy key infrastructure on their way back north. Such things as bridges and railroads were flagged for demolition.