There were about 26 countries during WWI.
forty
The Allied Nations fought against the Axis Powers. This was the United Kingdom, France, the United States, Canada, Australia and Soviet Union. Many other nations also sided with the Allied Nations.
forty
One of the Allied countries who did not join the League of Nations was the United States. Hope this helps, but this may not be the complete answer!
They have good relations with many nations because they generally try not to tick off the other nations that they like.
Two: US & Japan
Allied Powers
The protagonists and antagonists were the Allied nations and the Axis nations.
american
in Germany
forty
Assuming you are referring to WWII, the Allied nations fought the Axis nations, who at the beginning of the war were Germany, Italy, and Japan. Italy was eventually turned into an ally of the US and UK once Mussolini was taken out of power.