Which of the following was considered the turning point in American opinion about World War II?

WASHINGTON, D.C. -- On Sept. 1, 1939, after previously seizing Austria and Czechoslovakia, Nazi Germany invaded neighboring Poland, resulting in Britain and France declaring war on Germany and thus kicking off World War II in Europe.

U.S. Support for Poland, to a Point

As all of this was unfolding, in a poll conducted Sept. 1-6, 1939, Gallup asked Americans to what degree they supported assisting England, France and Poland. Americans supported providing material assistance to these three countries but were overwhelmingly opposed to sending military forces to fight Germany.

Americans' Support for Assisting England, France and Poland

How far should we go in helping England, France and Poland ...

In a separate question in the same 1939 poll, Americans were specifically asked if the U.S. should declare war on Germany in support of England, France and Poland and should deploy forces to assist those countries. Americans were strongly opposed, with 90% rejecting the idea and 8% in favor.

Americans' Views on Peace in Exchange for Poland in 1939

Less than two weeks after Germany's invasion of Poland, Gallup asked Americans about two options for trading Poland's independence for peace with Adolf Hitler. The American public resoundingly rejected both options, with 69% saying no to trading part of Poland for peace and 76% disapproving of exchanging the entire country to cease hostilities.

Americans Rejected Exchanging Poland for Peace in 1939

In addition to rejecting appeasement, a majority of Americans in September 1939 perceived Germany as a serious threat to the U.S. When asked if Germany would eventually attack the U.S. in the event that England, France and Poland lost the war, 58% of Americans thought it would. Fewer than four in 10, 35%, did not believe Germany would attack the U.S. "sooner or later" if the Allies were defeated.

More Americans Favored Peace for Territory in 1940

In February 1940, after Poland had fallen, Gallup again asked Americans for their views on accepting German conquests in exchange for peace with the Nazis. More than half, 53%, opposed allowing the Germans to keep Czechoslovakia in exchange for peace, and 63% said the same about Poland.

Americans' Views on Trading Territory for Peace With Hitler in 1940

In line with Americans' opinions on the issue, neither the U.K. nor France would offer to trade Poland or any other occupied territory to the Nazis in exchange for peace. In May 1940, German forces invaded and conquered both France and the Low Countries, rendering moot any question of trading Poland for peace.

The war continued -- and four days after Japan attacked U.S. forces at Pearl Harbor on Dec. 7, 1941, Germany declared war on the United States, bringing the country into World War II.

The widespread prosperity of the 1920s ended abruptly with the stock market crash in October 1929 and the great economic depression that followed. The depression threatened people's jobs, savings, and even their homes and farms. At the depths of the depression, over one-quarter of the American workforce was out of work. For many Americans, these were hard times.

The New Deal, as the first two terms of Franklin Delano Roosevelt's presidency were called, became a time of hope and optimism. Although the economic depression continued throughout the New Deal era, the darkest hours of despair seemed to have passed. In part, this was the result of FDR himself. In his first inaugural address, FDR asserted his "firm belief that the only thing we have to fear is fear itself--nameless, unreasoning, unjustified terror." As FDR provided leadership, most Americans placed great confidence in him.

The economic troubles of the 1930s were worldwide in scope and effect. Economic instability led to political instability in many parts of the world. Political chaos, in turn, gave rise to dictatorial regimes such as Adolf Hitler's in Germany and the military's in Japan. (Totalitarian regimes in the Soviet Union and Italy predated the depression.) These regimes pushed the world ever-closer to war in the 1930s. When world war finally broke out in both Europe and Asia, the United States tried to avoid being drawn into the conflict. But so powerful and influential a nation as the United States could scarcely avoid involvement for long.

When Japan attacked the U.S. Naval base at Pearl Harbor, Hawaii, on December 7, 1941, the United States found itself in the war it had sought to avoid for more than two years. Mobilizing the economy for world war finally cured the depression. Millions of men and women joined the armed forces, and even larger numbers went to work in well-paying defense jobs. World War Two affected the world and the United States profoundly; it continues to influence us even today.