World War I involved one group of countries fighting another.
The Central Powers ( Mittelmächte Központi hatalmak İttifak Devletleri or Bağlaşma Devletleri Централни сили Tsentralni sili ) , consisting of Germany , , the Ottoman Empire and Bulgaria -- hence also known as the Quadruple Alliance ( Vierbund ) -- was one of the two main factions during World War I ( 1914 -- 18 ) . The Paris Peace Conference , also known as Versailles Peace Conference , was the meeting of the Allied victors , following the end of World War I to set the peace terms for the defeated Central Powers diplomats from more than 32 countries and nationalities . Triple Entente . At the start of World War I in 1914 , all three Triple Entente members entered it as Allies of World War I against the Central Powers , Germany and Austria-Hungary . World War I . The war drew in all the world 's economic great powers , assembled in two opposing alliances : the Allies ( based on the Triple Entente of the Russian Empire , the French Third Republic , and the United Kingdom of Great Britain and Ireland ) versus the Central Powers of Germany and Austria-Hungary . The border between France and Germany was heavily fortified on both sides so according to the Schlieffen Plan , Germany then invaded neutral Belgium and Luxembourg before moving towards France from the north , leading the United Kingdom to declare war on Germany on 4 August due to their violation of Belgian neutrality .