The Middle East played a large role in World War 1. Their sultan declared a military jihad (holy war) against France, Russia and Great Britain during World War 1.
Russia's home front during World War 1 was characterized by civil war. It was these internal conflicts that led to Russia's premature withdrawal from the war.
Japan had conflicts with China and Russia before World War one.
Austria-hungary attacked Serbia
The assassination of Archduke Franz Ferdinand of Austria-Hungary by Serbian nationalists.
Nationalism was a key factor in the Balkan crisis.
The conflict between Serbia and Austria -Hungary was founded on the need of Serbs of Austria-Hungary . Russia, the mother of all slavs, intervened for Serbia while Germany , being in an alliance with Austria-Hungary supported them. This caused war between the two alliances.
Answer this question… The United States
Though huge numbers of people were killed, no country managed to conquer much territory