In Battlefield 1, as with World War 1, there are a variety of factions (aka countries or "sides") which are involved in open combat. These factions often had changing, uneasy, or strange alliances, reflective of their geopolitical environments.
Factions
Triple Alliance/Central Powers
Austro-Hungarian Empire
The Austro-Hungarian empire was a constitutional union of the Austrian Empire and the Kingdom of Hungary that existed from 1867 to 1918. The Empire was ruled by two monarchs, the Austrian monarchy and the Hungarian monarchy, with a single autonomous region called the Kingdom of Croatia-Slavonia. It was ruled by the royal House of Habsburg.
They were part of the "Triple Alliance" or "Central Powers", made principally of the Austro-Hungarian Empire, the German Empire, and the Ottoman Empire, with additional member Bulgaria. They were in opposition against the "Triple Entente" or "Allied Powers", made principally of the Russian Empire, France, the United Kingdom, the Kingdom of Italy, the Empire of Japan, and the United States of America.
German Empire
They were part of the "Triple Alliance" or "Central Powers", made principally of the Austro-Hungarian Empire, the German Empire, and the Ottoman Empire, with additional member Bulgaria. They were in opposition against the "Triple Entente" or "Allied Powers", made principally of the Russian Empire, France, the United Kingdom, the Kingdom of Italy, the Empire of Japan, and the United States of America.
Ottoman Empire
They were part of the "Triple Alliance" or "Central Powers", made principally of the Austro-Hungarian Empire, the German Empire, and the Ottoman Empire, with additional member Bulgaria. They were in opposition against the "Triple Entente" or "Allied Powers", made principally of the Russian Empire, France, the United Kingdom, the Kingdom of Italy, the Empire of Japan, and the United States of America.
Tripe Entente/Allied Powers
Kingdom of Italy
They were part of the "Triple Entente" or "Allied Powers", made principally of the Russian Empire, France, the United Kingdom, the Kingdom of Italy, the Empire of Japan, and the United States of America. They were in opposition against the "Triple Alliance" or "Central Powers", made principally of the Austro-Hungarian Empire, the German Empire, and the Ottoman Empire, with additional member Bulgaria.
United Kingdom
They were part of the "Triple Entente" or "Allied Powers", made principally of the Russian Empire, France, the United Kingdom, the Kingdom of Italy, the Empire of Japan, and the United States of America. They were in opposition against the "Triple Alliance" or "Central Powers", made principally of the Austro-Hungarian Empire, the German Empire, and the Ottoman Empire, with additional member Bulgaria.
United States of America
They were part of the "Triple Entente" or "Allied Powers", made principally of the Russian Empire, France, the United Kingdom, the Kingdom of Italy, the Empire of Japan, and the United States of America. They were in opposition against the "Triple Alliance" or "Central Powers", made principally of the Austro-Hungarian Empire, the German Empire, and the Ottoman Empire, with additional member Bulgaria.
Ottoman Empire
They were part of the "Triple Entente" or "Allied Powers", made principally of the Russian Empire, France, the United Kingdom, the Kingdom of Italy, the Empire of Japan, and the United States of America. They were in opposition against the "Triple Alliance" or "Central Powers", made principally of the Austro-Hungarian Empire, the German Empire, and the Ottoman Empire, with additional member Bulgaria.