Short answers, pulled from the story.
The Oster conspiracy was a plot within the German military to remove Adolf Hitler from power if his pressure on Czechoslovakia led to war. It represented the highest point of organized German anti-war activity. No comparable plan was developed for the invasion of Poland.
In September 1939-90% of Americans opposed declaring war on Germany, and 84% opposed deploying forces abroad to fight. By March 1940-96% were against entering the war. After the attack on Pearl Harbor in December 1941, nearly all noninterventionist organizations reversed course.
The America First Committee was the leading organization, with Charles Lindbergh as its most famous representative. The Keep America Out of War Congress, founded on the 6th of March 1938, had earlier been the only national body opposing all foreign intervention. Henry Ford, Father Charles Coughlin, and Senator Gerald Nye of North Dakota were among the most prominent individual voices.
Before June 1941, Communist parties worldwide opposed the Allied war effort following the Molotov-Ribbentrop Pact between Stalin and Hitler in August 1939. On the 22nd of June 1941, Germany's invasion of the Soviet Union in Operation Barbarossa reversed that stance overnight. Communist parties then became advocates for full material support to the Soviets.
Gandhi led the Quit India Movement to obstruct British war preparations and to demand complete independence from colonial rule. His aim was to prevent India from being drawn into a war he considered Britain's own to fight. The movement pursued its goals through non-cooperation rather than armed action.
Both Germany and Japan framed the war as a source of national shame. Germany moved toward a subdued nationalism in response, while Japan adopted formal pacifism as a political identity. The smaller Axis partners, Italy and Hungary, continued to debate whether they had been primarily victims or perpetrators of the conflict.