HistoryIn the aftermath of the 1848 Hungarian Revolution and the Austro-Prussian War of 1866, the Austrian Empire and the Kingdom of Hungary (both ruled in a personal union by the Emperor of Austria) were weakened. On 1 March 1867, the Austrian Empire and the Kingdom of Hungary (led in union by Emperor Franz Joseph I of Austria) signed the 1867 Compromise, which established a real union between the two countries. The armed forces were united under the Emperor-King and foreign affairs, defense, and finance were decided by him, while Austria and Hungary had separate prime ministers and parliaments.
Austria-Hungary consisted of several present-day countries, ruling over much of central Europe and eastern Europe, owning the region of Czechoslovakia, southern Poland, and Galicia (the western half of Ukraine) to the north, while to the south they owned much of the Balkans (including Bosnia and Herzegovina, Montenegro, Croatia, and Slovenia) in addition to Transylvania (the mountainous region of western Romania and eastern Hungary).
The dual monarchy of Austria-Hungary, a Great Power along with the Russian Empire, German Empire, United Kingdom, France, and the United States, was one of the strongest countries on the planet. They allied with Germany in the Austro-German Alliance of 1878-1918, joined the German and Russian empires in the Three Emperors' Alliance in 1881-1887, an alliance with the Kingdom of Serbia in the 1881-95 Austro-Serbian Alliance, the Kingdom of Italy and Germany in the 1882-1915 Triple Alliance, and the Austro-German-Romanian Alliance of 1883-1916. They consolidated their positions in Europe with these alliances, although some were very brief. The Three Emperos' Alliance ended in 1887 because of Austria-Hungary and Russia's conflicting interests in the Balkans, and the alliance with Serbia ended for similar reasons in 1895. Austria-Hungary expanded its non-European empire by annexing Tianjin in China as a colonial concession in 1901 following the Boxer Rebellion, during which it sent marines to guard its embassy to the Qing Dynasty. It also sent the Austro-Hungarian Navy and some troops to assist in the quelling of the xenophobic Boxers and the Qing Army.Austria-Hungary became a threat to the Balkans starting in 1878, when it occupied Bosnia and Herzegovina after some resistance from Bosniak Muslims - Austria-Hungary was given the right to occupy the region by the Congress of Berlin, which followed the Third Russo-Turkish War. Austria-Hungary created a crisis in 1909 when they annexed Bosnia and Herzegovina into their empire. The Russian Empire planned to invade Bosnia to prevent Austria-Hungary from adding Bosnia to their empire, but international opinion prevented them from doing so. However, the Kingdom of Serbia backed Bosnian resistance movements against the Austro-Hungarians, and Austria-Hungary had to deal with Slav nationalism. In both the Balkans and Czechoslovakia/Poland, Austria-Hungary had to fight against rebel nationalists.
On 28 June 1914, Archduke Franz Ferdinand and Archduchess Sophie of Hohenberg of Austria-Hungary were assassinated in Sarajevo, Bosnia by Serbian-backed Black Hand/Young Bosnia nationalist Gavrilo Princip. Austria-Hungary decided to finally destroy Serbia to prevent further attacks against their possessions in Bosnia, and along with the German Empire, they declared war on Serbia on 28 July 1914. The Russian Empire mobilized 12,000,000 troops to support their Serbian allies, so Germany preemptively declared war on them. They also had to declare war on France, which mobilized in support of their Russian allies. With France at war, the United Kingdom was also pressured to join due to a secret alliance, but they refused to join at first. Germany decided to invade France through neutral Belgium as a part of the Schlieffen Plan, and when Belgium's neutrality was violated, the United Kingdom decided to join the war. Germany and Austria-Hungary were known as the "Central Powers", while France, Britain, and Russia and their allies were known as the "Entente Powers" or the Allied Powers. With several great powers on both sides at war, the conflict became known as the "Great War", and later, World War I.Austria-Hungary mobilized 7,800,000 troops from across its empire, and its leadership fell into the hands of Chief-of-Staff Conrad von Hotzendorf. The Austro-Hungarian forces were too far away from the Low Countries to fight against the British and French in Belgium and France, but as they were on the border with Russia, they were on the front lines of the Eastern Front. The Austro-Hungarian army, poorly-trained and poorly-equipped, were repeatedly defeated in Galicia by the similarly bad Imperial Russian Army, but German reinforcements helped the Austrians and Hungarians in defending Galicia, and the two armies managed to conquer much of Russian Congress Poland. Ausria-Hungary struggled on the front with the Kingdom of Serbia at this time, and they were unable to win the war by Christmas.
In 1915, the war broadly changed. On 10 May 1915, Austria-Hungary launched the Gorlice-Tarnow Offensive, which destroyed several Russian armies and opened the road for the further conquest of Italy. With the assistance of Germany and their new allies of the Tsardom of Bulgaria, the Austro-Hungarians overran Serbia. However, on 21 May 1915, Italy entered the war on the side of the Allies, planning to conquer their cores of South Tyrol and Austrian Veneto. The Austro-Hungarian army engaged in a stalemate with the Royal Italian Army on the Trentino front in northern Italy and on the Isonzo River in Veneto, and they contained several Italian offensives there (11 offensives by 1917). The Austro-Hungarians continued to suffer defeats on the Eastern Front, so they let Germany take command of their forces there as they focused on crushing Italy.However, Austria-Hungary fought a larger amount of battles in 1916. The Russian Brusilov Offensive was carried out against the Austro-Hungarians in Galicia, and their armies were pushed back with heavy losses, although the Russian armies also took heavy casualties and the offensive was stopped only by German forces. The German and Austro-Hungarian forces were successful in conquering the Kingdom of Romania, which entered the side of the Allies in late 1916, but the French and British sent reinforcements to the Balkans to assist the homeless Serbian armies in Macedonia. The Kingdom of Montenegro joined the war on the Allied side, so the Austro-Hungarians occupied the country. 1917 brought the Kingdom of Greece and the United States into the war against Austria-Hungary, and Greek, French, and British troops fought against Austria-Hungary in the Balkans. The Austro-Hungarian forces won the Battle of Caporetto under German leadership that year, but the Italians recovered and continued to defeat Austro-Hungarian forces along the Isonzo. Austria-Hungary was able to withdraw its forces from the Eastern Front after the Russian Empire was overthrown in the Russian Revolution by the Bolsheviks under Vladimir Lenin, and the Austro-Hungarian forces concentrated on Italy and the Balkans.
Despite their victory over Russia, Austria-Hungary's armed forces became war-weary. From 15-23 June 1918, Austrio-Hungarian forces were defeated at the Battle of the Piave River by 580,000-1,740,000 Italian troops, with 175,000 Austro-Hungarian troops of 570,000-1,710,000 troops being killed, wounded, or captured in the battle. From 24 October to 3 November 1918, Austria-Hungary's army of 610,000-1,830,000 troops was destroyed by an Italian, British, French, Czechoslovakian, and American army at the Battle of Vittorio Veneto, where 35,000 Austro-Hungarian troops were killed or wounded and 426,000 troops were captured by the Allies. On 31 October, before the defeat ended, Hungary underwent a revolution, and Emperor Charles I of Austria, who had been reigning for just two years after Franz Joseph's death, ordered the dissolution of the Hungarian forces. On 11 November 1918, the day of the armistice with the Allied Powers that ended World War I, Austria-Hungary began to dissolve. The revolution that occurred resulted in the destruction of the country, and it divided into the Austrian First Republic, Hungarian Democratic Republic, Kingdom of Yugoslavia, Kingdom of Montenegro, Kingdom of Albania, Interwar Czechoslovakia, and Interwar Poland. Austria-Hungary was formally dissolved in 1920 in one of the last peace treaties following World War I, although by then it had already been practically dissolved.