Officially, World War 2 started when Germany invaded Poland on 1 September 1939. On 3 September 1939, Britain and France declared war on Germany.
23 nations.
The League of Nations was formed after World War 1 and fell apart as a reslt of World War 2. The United Nations formed toward the end of World War 2, initially as an organization of nations opposed to the Axis Powers.
the USSR and the US
Nearly all the major nations were involved in World War 2.
The USSR, and the United States of America.
The US, Spain, Switzerland, Turkey, Portugal, Sweden
great britain and france
Those nations not involved, were glad they weren't.
It was a World War and few nations and only the Antarctic Continent seemed able to avoid it effects.
the first world war was initially against Germany
Britain and Francee were involved in the Suez War.
many nations were involved in WW I. Hence the name.