World War I deepened the antagonism between the Germans and the Czechs within the Czech Lands. The Germans lent full support to the war effort of the Central Powers, but among the Czechs the war was unpopular, because they realized that a German victory would terminate their hopes for political autonomy. However, Czech opposition to the war was uncoordinated. The Young Czech leader Karel Kramář, a neo-Pan-Slavist himself, desired Russian troops to occupy the Czech Lands and install a Russian grand duke as the future king of Bohemia. His future political rival, Tomáš Masaryk, preferred a pro-Western orientation.

In exile in western Europe, Masaryk was joined by Edvard Beneš and Milan Štefánik. Masaryk, envisioning a political union of the Czechs and the Slovaks, established contacts with Czech and Slovak emigrants living in Allied and neutral countries, especially the United States. In October 1915, in a public lecture at King’s College, London, he called for the establishment of small states in east-central Europe, based on the principles of nationality and democracy and directed against German plans for European hegemony. He argued that divided nationalities, such as the Poles living in three countries and the Czechs and Slovaks living in two, should be allowed to form nation-states and become allies of the West. In 1916 the Czech National Council (later renamed the Czechoslovak National Council) was established in Paris under Masaryk’s chairmanship. Its members were eager to maintain contacts with the leaders at home in order to avoid disharmony, and an underground organization called the “Maffia” served as a liaison between them.

At home under Austrian rule the influence of the military increased. The press was heavily censored, public meetings were forbidden, and those suspected of disloyalty were imprisoned. Among the leading politicians who were arrested and received suspended death sentences were Karel Kramář and Alois Rašín. Dissatisfaction among the Czech soldiers on the Eastern Front became more articulate in 1915, and whole units often went over to the Russian side.

Francis Joseph died in November 1916 and was succeeded by Charles (I). The new emperor called the parliament to session in Vienna and granted amnesty to political prisoners such as Kramář and Rašín. Charles’s reforms, although in many respects gratifying, called for more-intensive activities abroad in order to convince the Allied leaders that partial concessions to the Czechs were inadequate to the problems of postwar reconstruction. The position of the Slovaks was not improving either, as the Hungarian government refused to respect the principle of nationality.

Two major events coincided with Charles’s new course in home affairs and with his discreet exploration of the chances of a separate peace: the Russian Revolution (March 1917) and the U.S. declaration of war on Germany (April). In May 1917 Masaryk left London for Russia to speed up organization of a Czechoslovak army. While small units of volunteers had been formed in the Allied countries during the early part of the war, thousands of prisoners of war were now released from Russian camps and trained for service on the Allied side. A Czechoslovak brigade participated in the last Russian offensive and distinguished itself at Zborov (Ukraine) in July 1917. From the United States came material help and moral encouragement, though U.S. Pres. Woodrow Wilson’s early statements pertaining to the peace aims were rather hazy. But several weeks after the United States declared war on Austria-Hungary, President Wilson promulgated his celebrated Fourteen Points (January 1918), the 10th of which called for “the freest opportunity of the autonomous development” of the peoples of the Austro-Hungarian Empire.

After the Bolsheviks seized power in Russia, they made a separate peace settlement with Germany. The Bolshevik government then granted the Czechoslovak Legion—made up of those Czechs and Slovaks who had been fighting on the side of Russia—the freedom to leave Russia, but violent incidents that occurred during the evacuation led the Bolsheviks to order the legion’s disarmament. The legionnaires rebelled, however, and took over the Trans-Siberian Railroad. By challenging Bolshevik power, the legion contributed to the outbreak of the Russian Civil War.

The achievements of the Czechoslovak Legion, noticed favourably by the Western governments and press, gave the Czechoslovak cause wide publicity and helped its leaders to gain official recognition. Masaryk left Russia for the United States, where, in May 1918, he gained solid support from Czech and Slovak organizations. A declaration in favour of a political union of the Czechs and the Slovaks, containing a guarantee of Slovak rights to their own parliament, legislation, and administrative language, was issued at Pittsburgh, Pa., on May 31, 1918.

Throughout 1918, dealings with the Allies progressed more successfully. Added to the favourable publicity of the Siberian campaigns were increased activities at home demanding a sovereign state “within the historic frontiers of the Bohemian lands and of Slovakia” (the Epiphany Declaration; January 1918). An anti-Austrian resolution adopted at the Congress of Oppressed Nationalities, held in Rome in April, helped to disarm conservative circles in Allied countries that had opposed a total reorganization of the Danubian region. Eventually, France recognized the Czechoslovak National Council as the supreme body controlling Czechoslovak national interests; the other Allies soon followed the French initiative. On September 28 Beneš signed a treaty whereby France agreed to support the Czechoslovak program in the postwar peace conference. To preclude a retreat from the earlier Allied declarations, the Czechoslovak National Council constituted itself as a provisional government on October 14. Four days later, Masaryk and Beneš issued a declaration of independence simultaneously in Washington, D.C., and Paris.

Meanwhile, events were moving rapidly toward total collapse of the Habsburg monarchy. The last attempt to avert it, a manifesto issued by Charles on October 16, brought no positive results. Afterward, Vienna had no choice but to accept Wilson’s terms. A domestic political group called the Prague National Committee proclaimed a republic on October 28, and two days later at Turčiansky Svätý Martin (now Martin, Slvk.) a Slovak counterpart, the Slovak National Council, acceded to the Prague proclamation.