Pan-Slavism increase the sphere of the war since it sought to unify people of Slavic ancestry in many countries.
Pan-Slavism, a movement developed in the mid-19th century, refers to the political ideology pertaining to the advancement of integrity and unity for the Slavic-speaking peoples. Its main impact occurred in the Balkans, where non-Slavic empires had ruled the South Slavs for centuries.
Pan-Slavism aimed to unite the people of Slavic ancestry, to create one very large and strong Slavic nation.