In politics, left-wing or the left, on the left-right political spectrum, is associated with minority issues of ethnicity and class. The term has been associated, in varying degrees, with social (as opposed to classical) liberalism, modern American liberalism, social democracy, socialism, communism, Marxism, syndicalism, communalism, communitarianism, libertarian socialism, anarchism, left-libertarianism, some forms of populism, anti-colonialism, green politics, most forms of progressivism, and the Religious Left.
The left is generally secular. However, in some Roman Catholic countries there is a tradition of Liberation theology which focuses upon "social justice", and in some Protestant countries there is a tradition of Christian Socialism. Religious movements sometimes embrace left-wing politics (the U.S. civil rights movement is one such example), but these unions often revolve around specific political issues rather than a fundamental convergence.
In the first half of the twentieth century, the Old Left argued that differences in social class determined the nature of a society. Between the 1950s and 1960s, this perspective was broadened by the New Left to include the broad spectrum of cultural politics: anti-racism; affirmative action; feminism; environmentalism; and other minority causes.
Center-left, left of center, and left liberal refer to the left side of mainstream politics in liberal democracies. These support liberal democracy, representative democracy, some degree of private property rights and free markets, high spending on social welfare, extensive regulation of the economy, and some public ownership. Examples of center-left political parties include the British Labour Party, the New Zealand Labour Party, the American Democratic Party and the Social Democratic Party of Germany.
Whereas Soft left refers to reformist, democratic or parliamentary forms of socialism (for example, Irving Howe or the Tribune group), Hard left refers to socialists who advocate more radical change in society, such as the British politician Tony Benn or the Militant Tendency. Organizations described as the far left, for instance groups affiliated to the Fourth International adopt more radical versions of left-wing politics and are rooted in the politics of the "old left." Ultra-left organizations are those deemed to be on the most extreme left of the political spectrum, for example Italian autonomism.
Origins and history of the term
The term originates from the French Revolution, when liberal deputies from the Third Estate generally sat to the left of the president's chair, a habit which began in the Estates General of 1789. The nobility, members of the Second Estate, generally sat to the right. It is still the tradition in the French Assemblée Nationale for the representatives to be seated left-to-right (relative to the Assemblée president) according to their political alignment.
As this original reference became obsolete, the meaning of the term has changed, and is now used to denote a broad variety of political philosophies and principles. In contemporary Western political discourse, the term is most often used to describe forms of socialism, social democracy, or, in the sense in which the term is understood in the United States, liberalism.
In the United States, no avowedly Socialist or Communist party ever became a major player in national politics, although the Social Democratic Party of Eugene V. Debs and its successor Socialist Party of America (in the late 19th and early 20th centuries) and the Communist Party of the United States of America (in the 1930s) made some inroads. While many American "liberals" might be "social democrats" in European terms, few openly embrace the term "left"; in the United States, the term is mainly embraced by New Left activists, certain portions of the labor movement, and people who see their intellectual or political heritage as descending from 19th century socialist movements.
Some Greens deny that green politics is "on the left" as several green proponents of capitalism have proposed what they considered more efficient means to achieve their objectives; nonetheless, green economic policies are generally considered to be left-wing, and when they have formed political coalitions (most notably in Germany, but also in local governments elsewhere), it has almost always been with groups that classify themselves as on the left.
The left has traditionally been concerned with the lower classes and with combating oppression. Thus the industrial revolution saw left-wing politics become associated with the conditions and worker's rights in the new industries. This led to movements advocating social democracy, socialism and trade unionism. More recently, the left has criticized what it perceives as the exploitative nature of current forms of globalization, e.g. the rise of sweatshops and the "race to the bottom", and either has sought to promote more just forms of globalization, such as fair trade, or has sought to allow nation-states to "delink" or break free of the global economy.
Although specific means of achieving these ends are not agreed upon by different left-wing groups, almost all those on the left agree that some form of government or social intervention in economics is necessary, ranging from Keynesian economics and the welfare state through industrial democracy or the social market to nationalization of the economy and central planning.
Advocacy of government or social intervention in the market puts some of those on the left at odds with advocates of the free market.
War and revolution
Historically, the left have been opponents of imperialist and colonial wars, and have championed anti-colonial rebellions. Opponents argue however that from Napoleon onwards the left have generally supported military conquests by regimes of whom they approve e.g. the Soviet Union.
While some segments of the left are inspired by a strict adherence to pacifism, much left-wing opposition to war arises from anti-capitalist sentiment; in other words, leftists reject warfare when they believe that capitalists will benefit. Left-wing opposition to war is also often characterised by the internationalist belief that world's workers share common interests with one another, rather than with the powers governing their respective countries.
First and Second World Wars
The First World War triggered fierce debate among socialist groups as to the right response to take, with the leaderships of most socialist parties of the Second International supporting their governments, and a minority of socialists, such as Rosa Luxemburg and Lenin opposing the war as imperialist. Left-wing opponents to the war came together at the Zimmerwald Conference. The Bolshevik's responded to a revolt by soldiers against the First World War with promises of "bread, land and peace." These promises proved to be misleading however, because once the Bolsheviks seized power there was famine due to enforced collectivisation. At a time the Soviets put all their resources into efforts to defend their country from invasion, a period known as "War Communism."
As a result of the agreement between National Socialist Germany and the Soviet Union supporters of the USSR were instructed by Stalin to describe those who advocated military attacks upon Germany as capitalist warmongers, but when Hitler surprised Stalin by invading Communist occupied Poland overnight the majority of those on the left who had been opposed the war became supporters of military action against Germany and Japan.
Spanish Civil War
The Spanish Civil War was seen by many on the left as an important fight against the anti-communist governments of Italy and Germany. In response to the outbreak of war, some joined International Brigades or other left-wing militias organized by trade unions or communist parties. Others campaigned for arms embargoes and advocated intervention by the League of Nations.
The left and political violence
The political term left arose during the French Revolution, i.e. during a period of political violence. The political left has a variety of positions on the issue of violence. This has ranged from the pacificism of the Independent Labour Party or social democrats' faith in legal, peaceful means of social change to the advocacy of violence by the revolutionary left.
Among the advocates of violent revolution were the Narodniks in Russia in the late 19th and early 20th centuries. They sought to overthrow the oppressive authoritarianism of the Tsarist state by systematic attacks on the Tsar and his ministers, a strategy known as propaganda of the deed. Most libertarian socialists turned against the Narodniks' terrorism.
In the 1970s, various left-wing groups sprang up from the social movements of the time, such as Weathermen and the Symbionese Liberation Army in the U.S., the Angry Brigade in the UK, the Baader-Meinhof group in Germany, the Red Brigades in Italy and so on. These groups turned to acts of terrorism in order to either hasten what they deemed progress or in order to shock the populace into dissatisfaction with the status quo. They also considered armed struggle to be necessary from an anti-imperialist view point, targeting United States military bases in an attempt to oppose the Vietnam War. Except in cases where they drew upon existing conflicts, for example the Provisional IRA, they lacked political support, they were eventually dismantled by the state, which enacted anti-terrorism legislation to provide it with the "extraordinary means." 
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- Social democracy
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- Encyclopedia of the American Left, ed. by Mari Jo Buhle, Paul Buhle, Dan Georgakas, Second Edition, Oxford University Press 1998, ISBN 0-19-512088-4
- Lin Chun, The British New Left, Edinburgh : Edinburgh Univ. Press, 1993
- Geoff Eley, Forging Democracy: The History of the Left in Europe, 1850-2000, Oxford University Press 2002, ISBN 0-19-504479-7
- Marxism on Terrorism by John Molyneux
- Terrorism and Communism by Karl Kautsky
-  Leftism in India
- The Marxists Internet Archive (a free online Marxist library)
- The Political Compass an alternate view of the political spectrum
- Leftist Parties of the World List of present-day leftist parties and organizations of the world, with links to their websites.
- Revolutionary Left - A forum dedicated to the Far-Left wing