If you mean in WW1 than it's Russia.
Russia
Austria-Hungary's Archduke Franz Ferdinand was assinated by Serbian Extremists. After Serbia refuseds to turn in the extremists Austria-Hungary declared War on Serbia. Germany allied with A-H as Russia allied with Serbia, with more countries joining in later on in the War.
Austria-Hungary's Archduke Franz Ferdinand was assinated by Serbian Extremists. After Serbia refuseds to turn in the extremists Austria-Hungary declared War on Serbia. Germany allied with A-H as Russia allied with Serbia, with more countries joining in later on in the War.
Because Germany declared war on Serbia, russia mobilized its army to protect Serbia due to an old alliance
Austro-Hungarian Archduke Franz Ferdinand was assinated by Serbian nationalists. Austria declared war on Serbia. Russia, allied with Serbia, declared war on Austria, Germany declared war on Russia, England and France declared war on Both.
When AH declared war on Serbia on 28th June, Russia started to mobilize it's troops on it's borders. Then Montenegro on 5th august declared war on AH, to help their brothers. Because in that time almost all population of Montenegro declared themselves as Serbs.
Germany was allied with Austria-Hungary in 1914. Serbia was allied with Russia, and Russia was a member of the Triple Entente with France and Britain. When Austria declared war on Serbia after the assassination of Archduke Franz Ferdinand in Sarajevo. Russia declared war on Austria. Germany then declared war on Russia and subsequently on France and Britain.
Austria-Hungary declared war on serbia and Germany joined because it was allied with austria.
because he was heir to the Austrian-Hungarian Throne and was murdered by a serbian, so the hungarians (who were allied with Germany) declared war on Serbia who were allied with the Russians who were allied with great Britain and France and that's what started it.
The domino effect was when one country declared war on another, allied countries would get involved also eg. Austria-Hungary declared war on Serbia, Russia stepped in to help Serbia and then Germany stepped in to help Austria-Hungary and so on.. hope that helps :D
the alliance systems are one of the main causes that the war spread to so many countries. the war was originally between Austria-Hungary and Serbia. But, Russia was allied with Serbia so they began mobilizing for war. Germany was allied with Austria-Hungary so they declared war on Russia. Germany later declared war on France. To get to France, Germany went through Belgium. Belgium was allied with Britain so Britain declared war on Germany. this continued until many more countries became involved.
The Archduke of Austria Franz Ferdinand was assassinated by a Bosnian-Serb. In retaliation Austria-Hungary gave Serbia an Ultimatum of demands designed to destroy Serbia's influence in Bosnia. Serbia rejected the Ultimatum and Austria-Hungary declared war on Serbia. Germany was Austria-Hungary's ally and agreed to assist Austria-Hungary in the invasion of Serbia. Russia, fearing an invasion of Serbia would end it's own influence in the Balkans began to mobilize for war. As a result, Germany declared war on Russia.
In 2006. when Montenegro declared independence.