For most of World War I, Einstein remained at the University of Berlin completing, and then awaiting the confirmation of, his general theory of relativity. However, Einstein was also a staunch and outspoken opponent of the war. He was especially appalled by his fellow scientists who supported the war effort of their respective nations, including Otto Stern, Max Born, Walther Nernst, and Marie Curie. In October 1914, two months after the start of the war, Einstein heard news of the publication of the "Manifesto of the 93" (also known as "An Appeal to the Cultured World"), a document created by the German wartime propagandists to persuade the international intellectual community that the German government's invasion of Belgium and involvement in the war were justifiable. The manifesto was signed by ninety-three leading German intellectuals from various fields, including the physicist Max Planck, the painter Max Lieberman, and the poet Gerhart Hauptmann.
When Einstein learned of this document, he joined with a like-minded physician and friend, Georg Friedrich Nicolai, to draft a counter-manifesto. This counter-manifesto, entitled "An Appeal to the Cultured World," was a recommendation to avoid annexations and to create a durable system of peace for Europe. Although Einstein and Nicolai deliberately used general terms in order to appeal to a broad audience, the manifesto received very few signatures. After this failure, Einstein joined the New Fatherland League, a political association of men of varied backgrounds who supported an early end to the war and the establishment of an international organization to prevent future armed conflicts.
While working in Berlin in 1915, Einstein was approached by the Berlin Goethe League, a peaceable organization that wished to publish the scientist's views on the war effort. In October 1915, Einstein wrote a three-page article entitled "My Opinion of the War," in which he argued that the roots of war lie in the aggressive biology of males. Once again, he rejected all kinds of war and urged the creation of an international political order to promote peace. In the 1920s, he was invited to join the League of Nations Committee on Intellectual Cooperation, an international intellectual union founded by the French philosopher Henri Bergson. Although he was distrustful of the organization's bureaucracy, Einstein regularly attended the commission's meetings from 1924 to 1927. He remained a staunch pacifist, highly critical of nationalism and committed to the idea of a single world government free of a military. Throughout the 1920s, he participated in numerous peace campaigns and wrote articles on international peace and disarmament. By the late 1920s, disappointed by the League of Nations' failure to enforce disarmament and proscribe war, Einstein had became even more outspoken in his international pacifism.
Another important aspect of Einstein's politics during the 1920s was a strong belief in Zionism. Einstein was drawn to the Zionist cause as a result of the influence of Chaim Weizmann, a Russian Jew who had recently persuaded the British government to issue the famous Balfour Declaration, declaring its full support for the establishment of a national home for the Jewish people in Palestine. Although Einstein disliked Zionism's nationalist aspect, he was interested in the establishment of a Hebrew University in Palestine. After witnessing the anti-Semitism of the European university system, Einstein was determined to create a place where Jews could gain an education unrestrained by prejudice. He saw Israel as a cultural center of Jewry ratherr than a Jewish homeland or a Jewish state.
In 1921, Einstein accepted an invitation to participate in a fundraising tour in the United States for the Jewish Development Fund "Keren Ha-Yesod." He traveled with the Weizmanns and his wife Elsa and spoke passionately on behalf of the planned Hebrew University in Jerusalem. Einstein was well received in America, especially when he lectured on relativity. He spoke at universities in Columbia, Cleveland, Chicago, Princeton, and several other major cities. When the Hebrew University was finally established in 1923, Einstein delivered the inaugural address in Jerusalem. However, he became increasingly distressed by the way in which the University was organized: Einstein had envisioned an academically elite institution devoted to research of the highest scientific standards; instead, he found that the wealthy American Jews who had funded the University were more interested in creating a teaching institution at the undergraduate level. In 1928, Einstein resigned from the academic board as a sign of his disapproval.
Although he was angry at the way in which Hebrew University was developing, Einstein attended the sixteenth Zionist Congress in Zurich in 1929, where he spoke on behalf of the cultural unity of the Jewish people. Soon afterwards, when the newspapers reported serious Arab attacks on Jews in Jerusalem, Einstein called for a fair settlement based on both Arab and Jewish interests. He appealed to Weizmann to cooperate peacefully with the Arabs and suggested the creation of a secret council of four Jews and four Arabs to reconcile their differing views, an idealistic goal that was never achieved. In 1947, when the United Nations debated the future of Palestine, Einstein argued against the partition plan that would divide the land into two states, Arab and Jewish. As an alternative, he advocated a military-free zone for both peoples. In 1952, four years after Israel became a Jewish state, David Ben-Gurion, Israel's premier, offered Einstein the position of president of Israel. Although Einstein was deeply moved by the offer, he explained that he did not feel that he had the interpersonal skills for the job. Nonetheless, Einstein remained deeply committed to the welfare of Israel and the Jewish people for the rest of his life.