Russia Russia considered itself an ally and protector of Serbia. They saw them as fellow-Slavs, sharing the same alphabet, a similar language and the same Orthodox religion. read more
28 July: Austria-Hungary declares war on Serbia; 1 August: Germany declares war on Russia; 3 August: Germany declares war on France; 3 August: Germany invades Belgium; 4 August: Britain declares war on Germany; I've often seen people making the mistake of claiming that Russia declared war on Austria and/or Germany first, but that's not what happened. read more
Within a few more days, Britain, France and Russia (the Allies) were all officially at war with Germany and Austria-Hungary (the Central Powers). What had started as a small, local problem in the Balkans was turning into the biggest and most brutal war the world had ever seen. read more