Britain, France, and Russia, but Russia became an ally when they realized that Hitler had gone back on their promise. I do not know about France, but I am pretty sure.
Initially they did not ally with Russia because Russia had allied with Germany. Once Germany attacked Russia and broke the pact the Russians wanted to ally with Britain and France. They eventually did.
france
France went into World War 1 because it had an alliance with Russia. When Germany declared war on Russia, France went to help its ally.
Russia, France, America, Britain, and China. OH and Canada.
Germany failed to renew their treaty or promise they made with Russia in 18 something or other. therefore Russia was free to ally with the Allied forces(countries lke England, France, etc.)
Russia was Serbia's main ally during World War I. Russia had a powerful army and powerful allies as well.
Romania was an ally of United Kingdom, France, Italy, Russia etc.
The main ally of Serbia was Russia
Romania was an ally of France, Italy, United Kingdom, Russia etc.
Russia jumped in on Serbia's side, dragging in her ally, France, in the process. This triggered the German attack on France, which the Germans made by way of Belgium. Going through Belgium brought Great Britain in. So Russia, France, Belgium and Great Britain (and all her Commonwealth states and colonies).
The Final spark that started the war was the assassination of Archduke Franz Ferdinand on June 28th 1914, by Serbian activists. This mean that on July 28, Austria-Hungary declared war on Serbia. Now, here's the confusing bit; Russia, Serbia's Ally, orders full mobilisation of troops. This causes Germany, Serbia's Ally, to declare war on Russia on August 1st. Russia's Ally FRANCE now mobilise their troops. Germany declares war on France, too. Britain, allied to France, intervein and declare war on Germany.