The First Balkan War lasted from October 1912 to May 1913 and involved actions of the Balkan League against the Ottoman Empire. The Balkan states' combined armies overcame the initially numerically inferior and strategically disadvantaged Ottoman armies, achieving rapid success.
The Second Balkan War was a conflict that broke out when Bulgaria, dissatisfied with its share of the spoils of the First Balkan War, attacked its former allies, Serbia and Greece, on 16 (O.S.) / 29 (N.S.) June 1913. Serbian and Greek armies repulsed the Bulgarian offensive and counterattacked, entering Bulgaria. With Bulgaria's also having previously engaged in territorial disputes with Romania and the bulk of Bulgarian forces engaged in the south, the prospect of an easy victory incited Romanian intervention against Bulgaria. The Ottoman Empire also took advantage of the situation to regain some lost territories from the previous war. When Romanian troops approached the capital Sofia, Bulgaria asked for an armistice, resulting in the Treaty of Bucharest, in which Bulgaria had to cede portions of its First Balkan War gains to Serbia, Greece and Romania. In the Treaty of Constantinople, it lost Adrianople to the Ottomans.
The Battle of Slivnitsa was a victory of the Bulgarian army over the Serbians on 17–19 November 1885 in the Serbo-Bulgarian War. It solidified the unification between the Kingdom of Bulgaria and Eastern Rumelia.
The Bulgarian First Army was a Bulgarian field army during the Balkan Wars, World War I and World War II.
The Battle of Sorovich took place between 21–24 October 1912 (O.S.). It was fought between Greek and Ottoman forces during the First Balkan War, and revolved around the Sorovich (Amyntaio) area. The 5th Greek Division which had been advancing through western Macedonia separately from the bulk of the Greek Army of Thessaly, was attacked outside the village of Lofoi and fell back to Sorovich. It found itself to be heavily outnumbered by an opposing Ottoman force.
The Battle of Monastir took place near the town of Bitola, Macedonia during the First Balkan War, between Serbian and Ottoman forces from 16 to 19 November 1912. It resulted in a Serbian victory after heavy fighting north of the city, the routed Turks fled abandoning their guns.
The Macedonian front, also known as the Salonica front, was a military theatre of World War I formed as a result of an attempt by the Allied Powers to aid Serbia, in the autumn of 1915, against the combined attack of Germany, Austria-Hungary and Bulgaria. The expedition came too late and with insufficient force to prevent the fall of Serbia and was complicated by the internal political crisis in Greece. Eventually, a stable front was established, running from the Albanian Adriatic coast to the Struma River, pitting a multinational Allied force against the Bulgarian army, which was at various times bolstered with smaller units from the other Central Powers. The Macedonian front remained stable, despite local actions, until the Allied offensive in September 1918 resulted in Bulgaria capitulating and the liberation of Serbia.
The Kosovo offensive of 1915 was an offensive launched as part of the Serbian campaign of 1915. It involved the Central Powers and the Kingdom of Serbia.
The Battle of Dobro Pole, also known as the Breakthrough at Dobro Pole, was a World War I battle fought between 15 and 18 September 1918. The battle was fought in the initial stage of the Vardar Offensive, in the Balkans Theatre. On 15 September, a combined force of Serbian, French and Greek troops attacked the Bulgarian-held trenches in Dobro Pole, at the time part of the Kingdom of Serbia. The offensive and the preceding artillery preparation had devastating effects on Bulgarian morale, eventually leading to mass desertions.
The Kingdom of Bulgaria participated in World War I on the side of the Central Powers from 14 October 1915, when the country declared war on Serbia, until 30 September 1918, when the Armistice of Salonica came into effect.
The Serbian Second Army was a Serbian field army that fought during the Balkan Wars and World War I.
The Battle of Kumanovo, on 23–24 October 1912, was a major battle of the First Balkan War. It was an important Serbian victory over the Ottoman army in the Kosovo Vilayet, shortly after the outbreak of the war. After this defeat, the Ottoman army abandoned the major part of the region, suffering heavy losses in manpower and in war materiel.
The Bulgarian Second Army was a Bulgarian field army during the Balkan Wars, World War I, and World War II.
The Monastir offensive was an Allied military operation against the forces of the Central Powers during World War I, intended to break the deadlock on the Macedonian front by forcing the capitulation of Bulgaria and relieving the pressure on Romania. The offensive took the shape of a large battle and lasted for three months and ended with the capture of the town of Monastir. On an average depth of 50km, the Bulgarian First Army gave battle on six occasions, being forced to retreat five times.
The Battle of Malka Nidzhe, also known as the Battle of Gornichevo was the opening battle of the Monastir Offensive. It lasted for three days and ended in victory for the Entente forces.
The Vardar offensive was a World War I military operation, fought between 15 and 29 September 1918. The operation took place during the final stage of the Balkans Campaign. On September 15, a combined force of Serbian, French and Greek troops attacked the Bulgarian-held trenches in Dobro Pole, at the time part of Serbia. The assault and the preceding artillery preparation had devastating effects on Bulgarian morale, eventually leading to mass desertions.
The Battle of Krivolak was a World War I battle, fought between 21 October and 22 November 1915. It was fought in the initial stage of the Macedonian campaign, in the Balkans Theatre. On 21 October, Bulgarian troops attacked the French-held positions near the Strumica rail station, at the time part of the Kingdom of Serbia, starting the battle. Fighting continued until 22 November, when two Serbian divisions failed to capture Skopje, thus rendering the continuation of Entente offensive operations dangerous and forcing the French to evacuate their forces from the region.
The Battle of Kosturino was a World War I battle fought between 6 and 12 December 1915. It was fought in the initial stage of the Macedonian campaign, in the Balkans Theatre. On 6 December, Bulgarian troops attacked the French and British-held trenches in Kosturino, at the time part of the Kingdom of Serbia. Though the early offensive was held in check, on 8 December, Bulgaria managed to infiltrate the Memesli ravine. Bulgaria then seized Crete Simonet, thus threatening to outflank the Allies. The Entente defeat at Kosturino led to the complete withdrawal of Allied forces from Serbia, thus enabling the Central Powers to build the Berlin to Constantinople rail line. In the meantime, the Allies concentrated on solidifying their defenses in Greece.
The Battle of Vranje, or the Liberation of Vranje, represented one of the final stages of the second phase of the Serbian–Ottoman War (1876–78). At the beginning of the war, the Serbian army began the offensive in what is today South Serbia. After the Battle of Grdelica, the Serbian army managed to break into the Masurica Valley leaving the road to Vranje open and unguarded. At the same time, many rebellions broke out in the Serbian-Ottoman border areas, including in the Vranje region, against Ottoman authority. To help the rebels, the Serbian command decided to send Lieutenant Stepa Stepanović to form a special rebel battalion.
The First Battle of Caribrod, was a battle of the Serbo–Bulgarian War fought on November 2, 1885 (O.S.) between the Royal Serbian Army and Bulgarian Army around Caribrod, today Dimitrovgrad, Serbia.
Kingdom of Serbia 
Ottoman Empire