World War One, Nations Involved
Austria-Hungary
| Declared war on Serbia .........July 28, 1914 |
| Declared war on Russia ........Aug 6, 1914 |
| Declared war on Belgium ......Aug 28, 1914 |
| Declared war on Portugal ......March 15, 1916 Belgium |
| Refused German ultimatum demanding permission for German troops to cross Belgium Aug 2, 1914 |
| Invaded by Germany .........Aug 3-4, 1914 Bolivia |
| Severed relations with Germany ........April 13, 1917 Brazil |
| Severed relations with Germany .....April 11, 1917 |
| Declared war on Germany .......Oct 26, 1917 Bulgaria |
| Declared war on Serbia .......Oct 14, 1915 |
| Declared war on Romania ......Sept 1, 1916 China |
| Severed relations with German .....March 14, 1917 |
| Declared war on Germany .....Aug 14, 1917 |
| Declared war on Austria-Hungary ....Aug 14, 1917 Costa Rica |
| Severed relations with Germany ....Sept 21, 1917 |
| Declared war on Germany ...May 23, 1918 Cuba |
| Declared war on Germany ....April 7, 1917 Ecuador |
| Severed relations with Germany ....Dec 8, 1917 France and their colonies |
| Invaded by Germany ......Aug 2, 1914 |
| Declared war on Austria-Hungary .....Aug 12, 1914 |
| Declared war on Turkey ....Nov 5, 1914 |
| Declared war on Bulgaria ....Oct 16, 1915 Germany |
| Declared war on Russia ....Aug 1, 1914 |
| Declared war on France ....Aug 3, 1914 |
| Declared war on Belgium ....Aug 4, 1914 |
| Declared war on Portugal .....March 9, 1916 Great Britain/Canada/Australia/and the remainder of the British Common Wealth and Empire including India. |
| Declared war on Germany ....Aug 4, 1914 |
| Declared war on Austria-Hungary ....Aug 12, 1914 |
| Declared war on Turkey ....Nov 5, 1914 |
| Declared war on Bulgaria ....Oct 15, 1915 Greece |
| Declared war on Austria-Hungary, Bulgaria, Germany and Turkey ....June 27, 1917 Guatemala |
| Declared war on Germany ....April 23, 1918 Haiti |
| Declared war on Germany ....July 12, 1918 Honduras |
| Declared war on Germany ....July 19, 1918 Italy |
| Declared war on Austria-Hungary .....May 23, 1915 |
| Declared war on Turkey .....Aug 21, 1915 |
| Declared war on Bulgaria .....Oct 19, 1915 |
| Declared war on Germany ......Aug 28, 1916 Japan |
| Declared war on Germany .....Aug 23, 1914 |
| Declared war on Austria-Hungary .....Aug 25, 1914 Liberia |
| Declared war on Germany .....Aug 4, 1914 Montenegro |
| Declared war on Austria-Hungary ....Aug 5, 1914 |
| Declared war on Germany .....Aug 8, 1914 |
| Declared war on Bulgaria .....Oct 15, 1915 Nicaragua |
| Declared war on Germany and Austria-Hungary .....May 8, 1918 Panama |
| Declared war on Germany ....April 7, 1917 |
| Declared war on Austria-Hungary .....Dec 10, 1917 Peru |
| Severed relations with Germany .....Oct 6, 1917 Portugal |
| See Germany and Austria-Hungary in this table Romania |
| Declared war on Austria-Hungary ....Aug 27, 1916 |
| Capitulated to Central Powers by Treaty of Bucharest .....May 7, 1918 |
| Re-entered the war on the side of the Allies ....Nov 10, 1918 Russia |
| Declared war on Turkey .....Nov 2, 1914 |
| Declared war on Bulgaria ....Oct 19, 1915 San Marino |
| Declared war on Austria-Hungary ....June 3, 1915 Serbia |
| Declared war on Germany .....Aug 6, 1914 |
| Declared war on Turkey .....Nov 2, 1914 Siam |
| Declared war on Germany and Austria-Hungary .....July 22, 1917 Turkey |
| Declared war on Romania ....Aug 30, 1916 |
| Severed relations with the US .....April 23, 1917 United States |
| Declared war on Germany ....April 6, 1917 |
| Declared war on Austria-Hungary ....Dec 7, 1917 Uruguay |
| Severed relations with Germany .....Oct 7, 1917 |
*** Much of Africa was held by European powers as colonies and thus Africans also willingly fought in World War One.
