In 1917 two separate events decisively changed the character of the war and set it on a course toward the rebirth of Poland. The United States entered the conflict on the Allied side, while a process of revolutionary upheaval in Russia weakened and then removed the Russians from the Eastern Front, finally bringing the Bolsheviks (see Glossary) to power in that country. After the last Russian advance into Galicia failed in mid-1917, the Germans went on the offensive again, the army of revolutionary Russia ceased to be a factor, and the Russian presence in Polish territory ended for the next twenty-seven years.

The defection of Russia from the Allied coalition gave free rein to the calls of Woodrow Wilson, the American president, to transform the war into a crusade to spread democracy and liberate the Poles and other peoples from the suzerainty of the Central Powers. Polish opinion crystallized in support of the Allied cause. Pilsudski became a popular hero when Berlin jailed him for insubordination. The Allies broke the resistance of the Central Powers by autumn 1918, as the Habsburg monarchy disintegrated and the German imperial government collapsed. In November 1918, Pilsudski was released from internment in Germany, returned to Warsaw, and took control as provisional president of an independent Poland that had been absent from the map of Europe for 123 years.

Data as of October 1992