Opposition to World War II
Opposition to World War II was most vocal during the early part of World War II, and stronger still before the war started. Some communist-led organizations with links to Comintern opposed the war during the period of the Hitler-Stalin pact but then backed it after Germany invaded the Soviet Union.
In Britain, Oswald Mosley and many members of the British Union of Fascists were opposed to a war with Nazi Germany, arguing that the Soviet Union was a greater threat to British freedom.  Mosley led a "Peace Campaign" to call for a negotiated peace with Germany. This campaign ended after Mosley and most active UK fascists were interned under Defence Regulation 18B in May 1940. 
Mohandas K. Gandhi's pacifist movement opposed the war even to the point of advocating that the British surrender, and that Jews offer only non-violent resistance to the Nazis. However, Gandhi still backed the use of Indian troops and territory in a pragmatic exchange for guaranteed Indian independence after the war.
The Catholic Worker Movement was also opposed to the war.
Socialists were divided in the 1930s. There was a strong element of pacifism in the socialist movement, for example in Britain's Independent Labour Party. The commitment to pacifism, however, was balanced by militant anti-fascism. During its Popular Front period, the Comintern allied with other anti-fascist parties, including right-wing parties. This policy was terminated by the Comintern when the Soviet Union signed a non-aggression pact with Hitler in August 1939.
The Communist front organizations opposed the war during the period of the Nazi-Soviet pact. Most dutifully followed orders from Moscow. In 1940, Britain's Daily Worker referred to the Allied war effort as "the Anglo-French imperialist war machine." At the same time, Joseph Stalin ordered a series of military attacks on Poland, Finland, Estonia, Latvia, Lithuania, and Romania. He used Communist parties and front groups to oppose the war and military preparations to prepare for the war in other countries so the Allies (Britain and France) were less able to resist aggression and to keep the US out of the war.
In the US, organizations like the American Peace Mobilization and veterans of the Abraham Lincoln Brigade protested in opposition to the war, conscription, and the Lend-Lease Act. They said of Lend-Lease, "Roosevelt needs its dictatorial powers to further his aim of carving out of a warring world, the American Empire so long desired by the Wall Street money lords."
Communist parties around the world reversed course when Germany invaded the Soviet Union on June 22, 1941, and then advocated that material support be extended to the Soviets.
A small number of socialists (but very few Comintern members, who obeyed Moscow) continued to oppose the war. Leon Trotsky had drawn up the Proletarian Military Policy, calling for opposition to the war and support for industrial action during it. Left communists took a similar position, as did many anarchists.
A few nationalist movements in colonial countries would take no part in the conflict, which they saw as one of the colonialists' making. This was perhaps strongest in India, where some nationalists went beyond opposition to the war to form the Indian National Army and fight alongside Japanese forces. Opposition was also seen among the Ceylonese garrison on the Cocos Islands which mutinied, in part due to the influence of the Trotskyist Lanka Sama Samaja Party.
Isolationism was strongest in the United States, where oceans separated it on both sides from the war fronts. Having seen their Wilsonian idealism for forgiveness for the Central Powers in World War I rejected, some Americans hoped to sit out this "Old World" war. The German-American Bund even marched down the avenues of New York demanding isolationism. The isolationists, led by the America First Committee, were a large, vocal, and powerful challenge to President Roosevelt's efforts to enter the war. Charles Lindbergh was perhaps the most famous isolationist. Isolationism was strongest in the Midwest with its strong German-American population.
- List of peace activists
- List of anti-war organizations
- Death to the Brutes, an anti-war anarchist poster printed in France during the Second World War
- The Culture of Fascism: Visions of the Far Right in Britain. Edited by Julie V. Gottlieb and Thomas P. Linehan I.B.Tauris, 2004. ISBN 978-1-86064-799-4 (p.67).
- Fascism in Britain: From Oswald Mosley's Blackshirts to the National Front by Richard C. Thurlow. I.B.Tauris, 1998, ISBN 978-1-86064-337-8 (p. 136-7).
- Mahatma Gandhi, Wikiquote
- Grenier, Richard, "The Gandhi Nobody Knows",[dead link] Commentary, March 1983
- "Reds, Labor and the War". TIME. May 13, 1940.
- Volunteer for Liberty, newsletter of the Abraham Lincoln Brigade, February 1941, Volume III, No. 2