Question

what countries were involved at the beginning of world war 2

Answer 1

Most historians mark the start of World War II as 1 September 1939, when Nazi Germany invaded Poland. The key countries involved at the very beginning were:

- Germany — launched the invasion of Poland on 1 Sept 1939.
- Poland — the country invaded on 1 Sept 1939.
- United Kingdom and France — both declared war on Germany on 3 Sept 1939 in response.
- British dominions and colonies — several joined the war with Britain right away or within days: Australia and New Zealand (3 Sept 1939), British India (as part of the British Empire, 3 Sept), South Africa (6 Sept), Canada (10 Sept).
- Soviet Union — invaded eastern Poland on 17 Sept 1939 under the Molotov–Ribbentrop pact with Germany.

Other major powers were involved slightly later or were already at war in related conflicts: Japan had been fighting China since 1937 (the Second Sino-Japanese War) and Italy remained officially neutral until it entered the war for the Axis in June 1940.

If you want, I can give a short timeline of the first weeks or list which countries were Axis and Allied members in 1939–1940.