In general terms, Zionism is the belief in a historical right to a homeland for the Jewish people in Israel. Variants have existed for centuries and continue to proliferate, but the core definition of modern Zionism is generally associated with the publication of Theodor Herzl's (1860 - 1904) The Jewish State in 1896, although the term, and indeed a philosophical discussion, seems to have been presented earlier by Nathan Birnbaum. In 1890, Birnbaum coined the terms “Zionist” and “Zionism,” and, in 1892, “Political Zionism.”
Herzl published it in the belief that antisemitism would never disappear; his views had been reinforced with his involvement in the affair of Alfred Dreyfus in France in 1894. Birnbaum and Herzl worked together at the First Zionist Conference, but developed ideological differences. Birnbaum had begun to question the political aims of Zionism and to attach increasing importance to the national-cultural content of Judaism. Birnbaum eventually left the Zionist movement and later became a leading spokesman for Jewish cultural autonomy in the Diaspora. Still, when a distinction is made, Herzl is often given credit for political Zionism as a subset.
Zionism is not monolithic; it was not monolithic prior to the establishment of the State of Israel. The leader of the Revisionist branch, Zev Jabotinsky (1880-1940) argued that the historic Jewish state was on both sides of the Jordan River; he is the founder of what became the modern Likud political party, but earlier argued for a distinct Jewish Legion fighting unit in World War I. Ahad Ha'am (1856-1927), however, articulated a spiritual Zionism, associated with renewal of Jewish culture and less focused on geography; his passion was worldwide education with limited settlement in Palestine. He felt that to settle there, one needed first to be a passionate religious Jew; it was not there as a place of physical safety.
Some regard it as appropriate for Jews scattered by the Biblical diaspora, while others see it perfectly practical to be a Jew in any liberal democracy other than Israel. Daniel Pipes, a strong Zionist associated with neoconservatism, makes the valid point that not all Jews are Zionists and not all Zionists are Jews. He goes on from what could be called a "hard-line" position, disapproving of non-Zionist Jews as "some openly hate Israel, others pretend it does not exist, and the most crafty of them present themselves as Zionist...That assumption also has two regrettable implications: it privileges anti-Zionists among them ("I'm Jewish but … ") even as it marginalizes non-Jewish Zionists." He advises, from a Zionist perspective, the language "Jews are adherents of a faith, not a political movement. When speaking of politics, talk about the pro-Israel community or Zionists, but not about Jews." Other Zionists regard the decision of an individual Jew not to be a Zionist as a personal, not political decision, without the flavor of disapproval.
Great Britain had control of the former Ottoman Empire areas that constituted Palestine. Partially in gratitude to Chaim Weizmann, a chemist who had made tremendous contributions to the British war effort, Foreign Secretary Arthur Balfour issued the 1917 Balfour Declaration, with the key language,
His Majesty's Government view with favor the establishment in Palestine of a national home for the Jewish people, and will use their best endeavors to facilitate the achievement of this object, it being clearly understood that nothing shall be done which may prejudice the civil and religious rights of existing non-Jewish communities in Palestine, or the rights and political status enjoyed by Jews in any other country. 
Great Britain, however, entered into other diplomatic agreements, some secret at the time, which overlapped the Balfour Declaration, such as the Sykes-Picot Agreement with France, the McMahon-Hussein Correspondence with the Mufti of Jerusalem, and the British White Paper of June 1922 amplifying on the McMahon-Hussin exchanges.
With the outbreak of World War I in 1914, Supreme Court of the United States Justice Louis D. Brandeis, who had become a Zionist, helped the World Zionist Organization move to the United States, becoming its chairman. While favoring creation of a Jewish homeland, he also recognized that Jews had found freedom and opportunity in the United States and therefore urged that Palestine be considered a homeland only for those Jews who wanted to go there. Nonetheless, American Jews, because of their safety and prosperity, should help secure and build that homeland. From 1914 to 1919, Brandeis was instrumental in raising millions of dollars for relief of war-afflicted Jews. He secured President Woodrow Wilson's support for the Balfour Declaration.
In 1919 he broke on issues of structural organization and financial planning with Chaim Weizmann, the leader of European Zionism. Weizmann defeated Brandeis for power and in 1921 Brandeis resigned from the Zionist Organization of America, along with his closest associates Rabbi Stephen S. Wise, Judge Julian W. Mack and Felix Frankfurter. He remained active in philanthropy directed at Jews in Palestine. In the late 1930s he endorsed illegal immigration to Palestine in an effort to help European Jews escape genocide when Britain denied entry to more Jews.
Zionists outside Israel
Many people support the Zionist movement but have no personal desire to emigrate to Israel, such as Justice Brandeis. Jews refer to the voluntary, spiritual decision to emigrate as "making aliyah"
Brandeis was of Jewish heritage but never practiced the religion. After mediating strikes involving Jewish garment workers, however, he became very aware of his cultural heritage. He did not always support Zionism. As of 1905, he believed in total assimilation of Jews into American society, a position subsequently used by his opponents within the American Zionist movement to attack him personally. By 1914, he reversed the position, deciding there was something separate and unique to the Jewish race, which was one of the reasons he wanted them to be relocated to Palestine. He concluded that:
- "Assimilation is national suicide". There must be a land "where the Jewish life may be naturally led, the Hebrew language spoken, and the Jewish spirit prevail," and that land was "our fathers' land" -- Palestine.
While Albert Einstein was a supporter of Zionism in the cultural sense, he often expressed reservations regarding its application in terms of nationalism. During a speech at the Commodore Hotel in New York, he told the crowd "My awareness of the essential nature of Judaism resists the idea of a Jewish state with borders, an army, and a measure of temporal power, no matter how modest. I am afraid of the inner damage Judaism will sustain."
Zionism and the Holocaust
Obviously, emigration to then-Palestine was attractive to threatened Jews.
While Zionist organizations had been fighting the British in Palestine, and supporting illegal immigration, there was a general recognition that the Nazis were an existential threat to Jews. Many of the Zionist forces fought on the Allied side.
Zionism and Israeli independence
Zionism, as mentioned, did involve various ways of fighting the British, well before the 1948 Arab-Israeli War following the UN Resolution creating modern Israel. Einstein signed a letter to the editor of the New York Times, condemning Menachem Begin and his nationalistic Herut party, especially for the treatment of the indigenous Arabs at Deir Yassin by Herut’s predecessor Irgun. 
Despite these reservations, he was active in the establishment of the Hebrew University in Jerusalem, which published (1930) a volume titled About Zionism: Speeches and Lectures by Professor Albert Einstein, and to which Einstein bequeathed his papers. In later life, in 1952, he was offered the post of second president of the newly created State of Israel, following Chaim Weizmann, but declined the offer, saying that he lacked the necessary people skills.
As a Jew in America, Einstein was closely associated with plans for what the press called "a Jewish-sponsored non-quota university," from August 19, 1946, with the announcement of the formation of the Albert Einstein Foundation for Higher Learning, Inc. until June 22, 1947, when he withdrew support and barred the use of his name by the foundation. The university opened in 1948 as Brandeis University.
Some Jews resident in Israel, such as the Edah HaChareidis, have theological objections to modern Zionism.
A number of organizations and countries, especially Third World, have criticized Zionism as racism. Israel responds that this is a double standard, citing examples such as the restrictions on non-Muslims in Saudi Arabia.
Christians and Zionism
One does not need to be a Jew to be a Zionist. British general Orde Wingate, while a Christian, trained the early Zionist forces in British Palestine and felt a spiritual connection. Nevertheless, there is a movement, among certain Christians, which makes Zionism, and often a one-state solution, part of their theology. Their desire is motivated by a belief that the return of Jews to Israel is a prerequisite for the return of Jesus Christ.
While Pipes wrote "other than the Israel Defense Forces, America's Christian Zionists may be the Jewish state's ultimate strategic asset," there is arguably a difference between Zionists who happen to be Christian or of any other faith, and Christian Zionists for which the role of Jews in Israel has a specific role in their theology.
According to Meyrav Wurmser, recognized as a hard-line Zionist supporter of the Israeli government, "Israel is today in the midst of a cultural civil war in which one side would like to see their country continue to exist as a Jewish state and the other believes that Zionism, the founding idea of the state, has reached its end. For the latter group, the time has come for Israel to enter its post-Zionist stage; for this reason, it describes itself as "post-Zionist."
Uri Davis is at the other extreme from Wurmser. He was the first to be elected to the Revolutionary Council of the Palestinian Fatah movement, once headed by Yasser Arafat. He is credited with originating the description of Israel, in the late 1980s, as an "apartheid state". He was part of the anti-Israel faction in the controversial He has been here before, not least as the man who first proposed the critique of Israel as an "apartheid state" in the late 1980s. He was part of the anti-Israel bloc in the UN World Conference Against Racism, the first meeting of which was in Durban in 2001 and whose language was later used as a basis for criticizing Barack Obama's award of the Medal of Freedom to Mary Robinson, by Jewish groups in the United States, including the Anti-Defamation League and American Israel Public Affairs Committee. He calls himself an "anti-Zionist
- Theodor Herzl (1896), The Jewish State, Mideast Web
- Nathan Birnbaum (Pseudonym: Mathias Acher), Jewish Virtual Library
- Vladimir Zeev Jabotinsky, Likud Herut (UK)
- Ahad Ha'am (1856-1927), Jewish Agency
- Daniel Pipes (18 August 2009), "Jewish" - Not the Same as "Pro-Israel"
- Paul Halsall, ed., Modern History Sourcebook: The Balfour Declaration
- The Sykes-Picot Agreement : 1916, Avalon Project, Yale University
- McMahon-Hussein Correspondence, 1915-1916, Mideast Web
- British White Paper of June 1922, Avalon Project, Yale University
- Speech of November 8, 1914, before the Menorah Society of Columbia University, cited in Mason, Alpheus T. Brandeis: A Free Man's Life (1946), online edition p 447
- Algemeiner.com - "The Death of Modern Zionism?", by Simon Jacobson
- Isidore Abramowitz, Hannah Arendt, Abraham Brick, Jessurun Cardozo, Albert Einstein, Herman Eisem, Hayim Fineman, M. Gallen, H. H. Harris, Zelig Harris, Sidney Hook, Fred Karush, Bruria Kaufman, Irma Lindheim, Nachman Maisel, Seymour Melman, Myer Mendelson, Harry Orlinsky, Samuel Pitlick, Fritz Rohrlick, Samuel Pitlick, Fritz Rohrlich, Louis Rocker, Ruth Sagis, Itzhak Sankowsky, I. J. Schoenberg, Irma Wolfe, Stefan Wolfe (2 December 1948), "Letter to the Editor: New Palestine Party Visit of Menachem Begin and Aims of Political Movement Discussed", New York Times
- Meyrav Wurmser (March 1999), "Can Israel Survive Post-Zionism?", Middle East Quarterly
- Anne E. Kornblut (August 12, 2009), "Honor for Former Irish President Draws Criticism", Washington Post
- Peter Beaumont (23 August 2009), "Why Israeli Jew Uri Davis joined Fatah to save Palestine", The Observer, Guardian (UK)