The Invasion of Poland marked the beginning of the Second World War in the West, and it was followed by the Soviet Invasion on the 17th. This invasion was inspired by the lost territory during WWI, and it finally brought U.S. congress to agree on shipping military aid to the Allies who seemingly did nothing about Hitler's land grabs at first. President Roosevelt was very against this, and he along with congress were heavily opposed to the Axis Powers with tensions rising ever more.
Involved: Poland, Germany, United States and Allied Forces
Outcomes: American Retaliation through Increased Aid, A more Visible War Effort to Combat Nazi Germany Taking Place, U.S. Congress taking more Notice on Issues in Europe