Modern Ruthenia traces back to the Kievan Rus, a Slavic state created after the Vikings invasions. The Rus were defeated and invaded by the Mongols, and after they retired, the conformation of the Kingdom of Poland took over these lands, until it became the Polish-Lithuanian Commonwealth. Ruthenia (Polish Ruś), was the name of several provinces of east-Slavic origin in the southern part of the Crown of Poland, but there was no administrative division composing all these governorships.
After the annexation of southern and central Russia in late 18th century, several parts of Russia were incorporated to the Crown as new Ruthenian provinces, while Muscovy and most of the territory was incorporated into Lithuania.
During the Great War of 1912, the Commonwealth was severely beaten by the Allied Powers, Lithuanian nationalism was a decisive factor to break the union, but Ruthenian and Russian nationalism were also important. This situation lead the Commonwealth to surrender in 1916, a couple of months earlier than co-belligerents Austria and France.
The Commonwealth had no functional government, but neither had the regions. During the Frankfurt conferences different alternatives were proposed on how to partition the Commonwealth. The Final proposal included to first follow the division between the Crown and Lithuania, and then, inside Lithuania, to secede pre-1768 Russia from Lithuania proper, and inside the crown to separate the west-Slavic territories (Poland) from the east-Slavic ones (Ruthenia).
The pact was signed in December 1917. In January 1918, Russia invaded Ruthenia to claim territories annexed by the Crown. The Ruthenian government agreed on the concessions.
Several Lithuanian provinces, usually known as White Ruthenia, had demanded either to be part of the Ruthenian state or to form their own state. After the Ruthenian defeat against Russia, White Ruthenian provinces demanded rather autonomy than annexation to the southern fellow country.
The tension grew, and the Lithuanian government massacred over 1000 non-combatant White Ruthenians in 1919. This triggered a war between Ruthenia and Lithuania, passively followed by the neighboring countries.
After three years of fighting, an almost defeated Lithuania finally broke the Ruthenian front. There was not a decisive military victory but Ruthenia finances were on the edge and the perspective of a longer war forced a collapse in the economy. Negotiations began, and the peace of Warsaw was signed between the fighting powers.
Lithuania transferred several White Ruthenian provinces to the Ruthenian Republic, but kept those closer to Vilnius.
Since this conflict, Ruthenia has suffered from both internal and external warfare, but none of them as costly as the war against Lithuania. Two civil wars (1938, and 1976), one secession war (1984), and wars against Russia (1923, 1956), Crimea (1923, 1981, 2002), Hungary (1975), and Poland (1929, 1956) for minor border conflicts. The last conflict was in 2002 against Crimea.