In the 1930's, Britain and France had a defence agreement with Poland. On 1 September 1939, German forces attacked Poland so on 3 September 1939, Britain and France declared war on Germany. The German attack on Poland is now accepted as the official start date of World War 2.
No.
no
In both.
Pearl Harbour.
yes
Germany
On Japan.
Any country can declare war on anybody else. What matters is can you back it up?
only on US
Switzerland was neutral.
Great Britian
neutral