WWI and WWII

Countries were involved in World War I

Central Powers:

• Germany
• Austria-Hungary
• Ottoman Empire
• Bulgaria

Allies and associated powers:

• Serbia
• Russia
• France
• Britain
• Belgium
• Romania
• US (entered in 1917 only after a German u-boat sunk a boat full of civilians) 
• The British Commonwealth countries: Australia, New Zealand, South Africa, India, etc. Canada was part of this group but was almost instantly looked upon as a rising superpower for it’s soldiers bravery and tactics, the Germans started calling them the "storm troopers" after they took Vimy Ridge (a vantage point previously thought impossible to take after numerous tries by the British and french) 
• Italy

 

Countries were involved in World War II

Allies Vs Axis Powers:

World War 2 involved most of the world’s nations which fought for either of two military alliances - the Axis Powers and the Allies. 
The key members of the Allies of World War 1 - France, Britain, Russia and the United States once again fought against Germany but they also had to fight against their former allies of Italy and Japan which joined the Nazi Germany. Just like World War 1, World War 2 started in Europe with the German invasion of Poland on September 1, 1939, which is traditionally viewed as the beginning of war. 

Countries that Joined the Allies:

Most of the countries of world joined the Allies although some of them were controlled by pro-Axis regimes. The original anti-German military alliance consisting of Poland, France and Britain was eventually joined by the following countries (by alphabetical order):

• Aden Protectorate (former South Yemen)
• Albania
• Argentina
• Australia
• Belgium
• Bolivia
• Brazil
• British Malaya (today’s Malaysia and Singapore)
• British Raj (today’s India, Bangladesh, Burma and Pakistan)
• Canada
• Chile
• China
• Colombia
• Costa Rica
• Cuba
• Cyprus
• Czechoslovakia
• Denmark
• Dominican Republic
• Dutch East Indies (present-day Indonesia and New Guinea)
• Ecuador
• El Salvador
• French Indochina (today’s Cambodia, Laos and Vietnam)
• French Guiana
• Greece
• Guatemala
• Guyana
• Haiti
• Honduras
• Iran
• Iraq
• Luxembourg
• Malta
• Mexico
• Mongolia
• The Netherlands
• Newfoundland
• New Zealand
• Nicaragua
• Norway
• Palestine
• Panama
• Peru
• Philippines
• Saudi Arabia
• Soviet Union
• Syria
• Trucial States (today’s United Arab Emirates)
• Turkey
• The United States
• Uruguay
• Venezuela
• Yugoslavia

The Allied coalition also included all African countries except for Italian colonies of Somalia, Ethiopia and Italian North Africa (present-day Libya), and Spanish and Portuguese colonies of Mozambique, Angola, Spanish Sahara (present-day Western Sahara) and Portuguese Guinea (today’s Guinea-Bissau) which were neutral like their colonial rulers. Countries such as Italy which later left the Axis powers and joined the Allies are not considered Allied states. 

States that Allied Themselves with the Axis Powers:

The Axis powers were officially founded by the Tripartite Pact signed between the Nazi Germany, Italy and Japan on September 27, 1940. Countries that allied themselves with the Axis powers include:

• Bulgaria
• Finland
• Hungary
• Romania
• Vichy France
• Thailand
• Formosa (present-day Taiwan)
• Manchuria

The Axis powers created a number of puppet states in occupied areas but they usually are not considered Axis states although some of them actively collaborated with the Axis such as the newly established Independent State of Croatia and the Slovak Republic. However, both of them ceased to exist after the end of World War 2 and were rejoined with Czechoslovakia and Yugoslavia, respectively, both of which were Allied states. 

Neutral Countries:

Few countries remained neutral during the entire World War 2:

• Switzerland
• Sweden
• Spain
• Portugal
• Iceland
• Ireland
• Afghanistan
• North Yemen
• Oman
• Nepal
• Tibet and the above mentioned Spanish and Portuguese colonies in Africa.