As the Great War rolled into its second year, it became obvious that Germany was caught in an unwinnable two-front war. Hoping to distract the Russians by deepening the revolution breaking out in early 1917, the German Foreign Minister Arthur Zimmerman arranged for a group of Communists including the infamous Vladimir Lenin to travel through German territory in a closed railroad car, eventually taking them back to Petrograd. To weaken the Western Front, Germany announced its resumption of unrestricted submarine warfare, crippling the supply line coming in from America.
President Wilson attempted to maintain a virtual peace by arming ships to destroy U-boats. Despite the Americans' merchant marines, the submarine attack proved overwhelmingly successful. It was only a matter of time before America would come into the war.
Seeing that the war might spread, German leadership began to investigate ways to make such an expansion work in their favor. Zimmerman sent a telegram to the ambassador to Mexico, Heinrich von Eckardt, instructing him to suggest an alliance. Germany would contribute munitions and funding while Mexico created a new front for America. By the time of Germany's victory, it would give Mexico back Arizona, New Mexico, and Texas, land lost in the Mexican-American War seventy years before. Mexico itself was in a very difficult position, still facing revolutionaries after decades of lawless fighting in the desert northwest. The US had already performed patrols into Mexico, chasing warlords such as Pancho Villa who raided American towns. Mexico adopted a new constitution on February 5, 1917, which was the first in the world to guarantee social rights. There was still much discontent in the country, and at last the Mexican government determined that solidarity could be established if the nation faced a single enemy. On April 6, 1917, the US Congress declared war on Germany and its allies, which suddenly included Mexico.
On the same day, the war spilled northward into the Baltic region. Despite its earlier prominence as one of the greatest nations of Europe, Sweden had long maintained its neutrality. Wars with Russia had weakened the country in the eighteenth century and resulted in the loss of Finland in 1809. In the Napoleonic Era, Norway was handed over to Sweden from Denmark, though the Norwegians fought for independence. In 1905, Norway won its independence, and Sweden became a fraction of what it had been. After much encouragement and seeing the weakness of the Russians, the Swedes finally determined to win back their glory by retaking Finland. On April 6, a Swedish force invaded from the north, backed by a flotilla, and was joined by hopeful Finns. "White" Finns who had enjoyed Russian protection in the Grand Duchy interrupted the Swedish advance, adding to the chaos.
Despite the entrance of the United States, 1917 proved a difficult year for the Allies. US troops were immediately dispatched to Mexico, which was quickly overrun thanks to armored vehicle advances made by effective military minds such as Captain George S. Patton. While the battles were one-sided, America became bogged down with long supply-trains and a difficult occupation. Revolutionaries who had long practiced guerrilla warfare continued their resistance, causing Americans to pour more and more troops into Mexico rather than the trenches in France.
Issues also broke out between the United States and Japan, who had been among the Allies since the first days of the War. Almost immediately after their declaration of war against Germany, Britain and Japan followed their treaty of 1902 to use Japanese ships to capture German colonies in the Pacific and destroy the Kriegsmarine stationed there. With Russia collapsing, the Japanese began to push further into Asia, bringing the question of expansion into China. The US had disapproved of the Twenty-One Demands issued by Japan to China, which Secretary of State William J. Bryan saw as a rejection of the previous Open Door Policy defending Chinese autonomy while supporting all foreign interests. Britain attempted to keep both sides happy and helped to clarify spheres of influence while hosting Japanese Foreign Minister Ishii Kikujiro and American Secretary of State Robert Lansing, promoting Japan while the US held the Philippines.
Russia dropped out of the war October 26, 1917, with the Treaty of Brest-Litovsk, forming a separate peace with Germany. While much of the Central Powers celebrated, the Russian Civil War proved to destabilize the conquered regions. As Socialist "Reds" expanded their powers in Russia following the November revolution, they crossed the border into Finland, creating a new front for the Swedes occupying there. The Swedish invasion turned into a multisided Finnish Civil War. After a Soviet victory in the Russian Civil War, the Swedes were chased out of Finland, which again fell under Russian dominance.
The exhausted Central Powers eventually collapsed in 1919, ending the fighting in Europe while it continued for years elsewhere. The American occupation of Mexico finally ceased in 1920, though it would forever mingle America in the affairs of Latin America. The ABC Nations (Argentina, Brazil, and Chile) worked to counter America’s Monroe Doctrine, causing division and a number of bush wars, such as the fierce fighting in America’s occupation of Hispaniola and expansion into the Caribbean.
When Germany went to war against Western Europe again in 1939, the United States refused to join another World War as occupations in the south were so difficult. The war did expand to Asia, however, when the Japanese allies of Germany performed a sneak-attack on Vladivostok in 1941. Soon both hemispheres were once again embroiled in war.
In reality, Mexico and Sweden maintained their neutrality in World War I. US intervention shifted more abroad, gradually away from a paternalistic stance of the Monroe Doctrine and toward the Truman Doctrine’s global Cold War.