Mark Henderson answered
There were a number of reasons why Britain got involved in World War One:
Central powers- 16,403,000 Killed missing or wounded in action:
- The neutrality of Belgium- Britain was committed to a neutral Belgium state. When Britain's ultimatum to Germany was rejected and the German empire invaded Belgium, Britain declared war. Belgium had been created to act as a buffer state between France and Germany, and so keeping the country intact and neutral was paramount to achieving a stable peace on the continent.
- The Triple Entente - Britain was part of a system of alliances known as the Triple Entente. This alliance was a collective defence pact between France, Russia and Britain, intended to counter the threat posed by the Central Powers (The German Empire, Austria-Hungary, Bulgaria and The Ottoman Empire). When the central powers declared war on France and Russia, this caused Britain to act.
- The balance of power in Europe - For hundreds of years Britain maintained the same policy towards the European powers. This involved keeping a stable balance of power on the continent so that, if one country attempted to dominate the continent (such as Napoleonic France), then Britain would intervene. Germany's new industrial, economic and military strength made it a threat to Britain's and Europe's security.
- France
- British Empire
- Russia
- Italy
- United States
- Romania
- Japan
- Serbia
- Belgium
- Greece
Central powers- 16,403,000 Killed missing or wounded in action:
- Germany
- Austria-Hungary
- Ottoman Empire
- Bulgaria