This is a difficult question to answer, because most historians would argue that World War II was a watershed moment for the Civil Rights Movement, for many reasons. To argue against this consensus, though, one might look at the realities of life in the Deep South, where the movement for civil rights met the most resistance. The war ended in 1945, and Southern cities (like Atlanta, Montgomery, Mobile, and New Orleans), their populations swollen by war industries, became crucibles for racial conflict. This was because thousands of African Americans had moved to these cities to take advantage of economic opportunities during the war. Southern cities responded by doubling down on Jim Crow (segregation) laws. Many of these would be directly challenged by African American activists (like, for example, Rosa Parks in Montgomery.) Even this line of argument suggests that World War II was an important impetus for civil rights. But looking at the situation through the eyes of an African American in the rural South, one might see little social change resulting from the war—indeed, things got worse before they got better. While civil rights workers protested segregation on public transport and at lunch counters, the vast majority of black men and women in the South remained desperately poor and lived in small rural communities. They would have seen very little change in the aftermath of the war. Even the most famous victories of the Civil Rights Movement came two decades after the end of World War II. So citing World War II as the "watershed" event in the Civil Rights Movement makes some assumptions that may seem simplistic. It falsely suggests that the urban black experience in the South was the dominant one. It suggests a certain inevitability that would not have been evident to people at the time. Finally, it oversimplifies the movement, which had many different facets and even factions.
https://www.history.com/topics/black-history/civil-rights-movement
While significant desegregation and nullification of Jim Crow laws would not take place until after World War II, the war years saw African Americans begin to nudge their way toward equality. Led by the charismatic President of the Brotherhood of Sleeping Car Porters, A. Phillip Randolph, civil rights groups of the early 1940s organized the first March on Washington as a protest to what they saw as a double standard in the country regarding race. On one hand, America was fighting for the world's freedom against a regime in Germany founded on racism. On the other hand, blacks were still treated as second-class citizens. They were treated as lesser than white soldiers, and they were often paid much less than white workers in the nation's defense industry.
Organizers estimated that over one hundred thousand marchers were prepared to descend on Washington DC in the summer of 1941. Alarmed by such a demonstration, President Franklin D. Roosevelt issued Executive Order 8802 which sought to eliminate prejudicial hiring in the defense industry. (The prior Democrat, Woodrow Wilson, oversaw unprecedented segregation in the federal government.) The order's title read, "Reaffirming Policy Of Full Participation In The Defense Program By All Persons, Regardless Of Race, Creed, Color, Or National Origin, And Directing Certain Action In Furtherance Of Said Policy."
Although it was just a baby step on the road to desegregation, the act was integral in later eliminating racial discrimination in all federal hiring. In 1948, the military followed suit by allowing black and white soldiers to serve side by side in the nation's armed forces. The 1941 March on Washington was ultimately cancelled because of the passage of Executive Order 8802. A more consequential March on Washington would take place in 1963 with Martin Luther King Jr. giving his famous "I Have a Dream" speech.
Perhaps the most consequential executive order involving civil rights took place early in 1942 when President Franklin Roosevelt, responding to hysteria over the Japanese attack at Pearl Harbor, signed Executive Order 9066 expelling those of Japanese ancestry from military areas "as deemed necessary and desirable." The resulting order caused the forced evacuation of 112,000 Japanese Americans to camps throughout the West Coast. Many established Japanese Americans lost their jobs, their businesses, their farms, and the respect from white Americans they had been fostering for many decades. Moreover, conditions in the relocation camps were poor and the Japanese often received brutal treatment from military guards. For nearly two years the United States government denied the rights of its own citizens, setting the trajectory of civil rights backwards.
In California, then-Governor Earl Warren was an early proponent of Roosevelt's "Removal Order," arguing vehemently that the West Coast needed to be kept safe from sabotage. He said, “If the Japs are released, no one will be able to tell a saboteur from any other Jap. . . . We don’t want to have a second Pearl Harbor in California. We don’t propose to have the Japs back in California during this war if there is any lawful means of preventing it.”
During the war, only ten Americans were convicted of spying for Japan. Warren, in his memoirs many years later, admitted that his treatment of the Japanese during the war had been wrong. He wrote that he had, over the years, come to regret "the removal order and my own testimony advocating it, because it was not in keeping with our American concept of freedom and the rights of citizens."
For more in-depth study on the internment during World War II, I would point to three excellent portrayals of the Japanese American problems of the time. First, Jeanne Wakatsuki Houston's Farewell to Manzanar is an effective memoir of her childhood in the relocation center in the California desert. Second, John Okada's No-No Boy is about a young Japanese man who refused to join the U.S. military and was sent to prison. Some Japanese American men did serve, especially in the famous 442nd Regiment in Europe. More than 800 Japanese Americans were killed in action. Finally, George Takei, of Star Trek fame, has penned an entertaining and revealing musical, Allegiance, about his experience as a child being uprooted from his family's farm in the Salinas Valley to the Heart Mountain Relocation Center in Wyoming.
https://www.blackpast.org/african-american-history/march-washington-movement-1941-1947/
https://www.theatlantic.com/politics/archive/2015/11/wilson-legacy-racism/417549/