No, Serbia was not part of Russia during World War 1. Serbia was an independent country that was allied with Russia during the war.
Russia was the first Allied Nation to mobilize troops against Austria-Hungary for its declaration of war on Serbia.
They allowed a small conflict between Serbia and Austria-Hungary (Austria-Hungary taking over Serbia) to quickly grow larger and involve Germany, Russia, France, and UK. Serbia had an alliance with Germany, and Serbia was allied with Russia and Russia was allied with France and the UK. Now you see how two countries dragged in four more countries. Further into the war, the US joined the Allied Powers (UK, France, Serbia, and Russia) and the Ottoman Empire and Bulgaria joined the Central Powers (Germany, Austria-Hungary).
Serbian nationalism increased tensions within Europe before World War I. Serbia wanted to create a pan-Slavic state in the Balkans which included Bosnia-Herzegovina, held by Austria-Hungary. Serbia was allied with Russia and Austria was allied with Germany. Russia allied with France. A war between Serbia and Austria threatened to involve the whole of Europe.
Serbia assassinated arch duke Ferdinand Austria attacked Serbia Russia attacked Austria because they were allied to Serbia Germany attacked Russia because Germany was allied to Austria France and England were allies of Russia, so Germany attacked France France was then in war with Germany
They allowed a small conflict between Serbia and Austria-Hungary (Austria-Hungary taking over Serbia) to quickly grow larger and involve Germany, Russia, France, and UK. Serbia had an alliance with Germany, and Serbia was allied with Russia and Russia was allied with France and the UK. Now you see how two countries dragged in four more countries. Further into the war, the US joined the Allied Powers (UK, France, Serbia, and Russia) and the Ottoman Empire and Bulgaria joined the Central Powers (Germany, Austria-Hungary).
Great Britain, France, Belgium, Russia. Russia backed Serbia. As Russia was allies with Britain and France through the triple entente, Serbia had their backing as well. Eventually, America and Belgium supported them too.
Russia was Serbia's main ally during World War I. Russia had a powerful army and powerful allies as well.
- England - France - Russia - Serbia - U.S. (joined in 1918)
At the begining of the war Serbia was allied with Montenegro, Russia and Greece. Greece stayed neutral in war, while Montenegro and Russia helped Serbia to fight with Austria-Hungary. When Serbo-Austrian war became World war Serbia alongside Russia and MOntenegro was part of Entante (Allies).
France and Great Britain allied with Serbian during World War 1. Serbia was the first country to be attacked in World War 1.
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.