What happened after Germany invaded Poland Who else joined the war?

After Germany invaded Poland on September 1, 1939, Britain and France declared war on Germany on September 3, marking the official start of World War II. Following the invasion, the Soviet Union invaded Poland from the east on September 17, 1939, as part of a secret agreement with Germany. This led to the partition of Poland between Germany and the Soviet Union. Other countries, including Australia, New Zealand, Canada, and later nations like Italy and Japan, would join the conflict, expanding the war further.