Declaration of War by Each Country



World War I broke out with Austria-Hungary’s declaration of war against Serbia in July 1914. Soon, most of the major nations of the world were involved in armed conflict. Countries such as Australia, Canada, India, and New Zealand joined in as part of the British Empire. Other colonies of European nations were also embroiled in conflict, thus bringing in most countries of Asia and Africa to the war.

YEAR DATE DECLARATION OF WAR
1914 28-Jul Austria-Hungary declares war on Serbia.
1-Aug Germany declares war on Russia
3-Aug Germany declares war on France
3-Aug Germany invades Belgium
4-Aug Britain declares war on Germany
5-Aug Montenegro declares war on Austria-Hungary
6-Aug Austria-Hungary declares war on Russia
6-Aug Serbia declares war on Germany
8-Aug Montenegro declares war on Germany
12-Aug France declares war on Austria-Hungary
12-Aug Britain declares war on Austria-Hungary
23-Aug Japan declares war on Germany
25-Aug Japan declares war on Austria-Hungary
28-Aug Austria-Hungary declares war on Belgium
2-Nov Russia declares war on the Ottoman Empire
2-Nov Serbia declares war on the Ottoman Empire
3-Nov Montenegro declares war on the Ottoman Empire
5-Nov France declares war on the Ottoman Empire
5-Nov Britain declares war on the Ottoman Empire
1915 23-May Italy declares war on Austria-Hungary
21-Aug Italy declares war on the Ottoman Empire
14-Oct Bulgaria declares war on Serbia
15-Oct Montenegro declares war on Bulgaria
15-Oct Britain declares war on Bulgaria
16-Oct France declares war on Bulgaria
19-Oct Italy declares war on Bulgaria
19-Oct Russia declares war on Bulgaria
1916 9-Mar Germany declares war on Portugal
15-Mar Austria-Hungary declares war on Portugal
27-Aug Italy declares war on Germany
27-Aug Romania declares war on Austria-Hungary
30-Aug Ottoman Empire declares war on Romania
1-Sep Bulgaria declares war on Romania
1917 6-Apr USA declares war on Germany
7-Apr Panama declares war on Germany
27-Jun Greece declares war with Austria-Hungary
27-Jun Greece declares war with Germany
27-Jun Greece declares war with Bulgaria
27-Jun Greece declares war with the Ottoman Empire
7-Dec USA declares war on Austria-Hungary
10-Dec Panama declares war on Austria-Hungary
1918 23-Apr Guatemala declares war on Germany
8-May Nicaragua declares war on Austria-Hungary
8-May Nicaragua declares war on Germany
12-Jul Haiti declares war on Germany
19-Jul Honduras declares war on Germany

 

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