Kingdom of Bulgaria

The Kingdom of Bulgaria was one of the Central Powers in World War I, and the last to join the alliance. In September 1915, the Kingdom entered the war in which it took part in the Balkans theatre. Initially successfully invading Serbia alongside Austro-Hungarian and German forces, Bulgaria spent much of the remainder of the war holding the vital Macedonian front against Entente forces in Northern Greece. Much of the reason for Bulgaria's entry into the war was the consequences of the Second Balkan War of 1912-13, in which Bulgaria was defeated by their Balkan neighbors, which now held territory, to which Bulgaria laid claim.

While the Macedonian front remained mostly stationary, the army and populace was suffering from slow attrition, and by the time the Entente went on the offensive in mid/late-1918, Bulgaria was starving and rife with political unrest, which was accelerated by the defeat at the battle of Dobro Pole 15th-18th September 1918. On 29 September, the Bulgarians were granted the Armistice of Salonica, leaving the southern flank of the Central powers exposed.