In 1753, the Habsburg monarchy under Emperor Anna Josepha found itself politically encircled and militarily overextended, facing threats from Prussia, Eastern Rome, and a restless Hungary. Seeking a lifeline, Vienna forged a secret defensive pact with Britain to counter potential French aggression. However, the spark for conflict arose in the east; following a series of border skirmishes, Austria declared war on Hungary in 1756, initiating a conflict known as the "Deluge." Although the Hungarians achieved early successes, the Austrian army eventually rallied to crush them near Vienna and occupied their territory. The war quickly widened as Eastern Rome intervened to support the Magyars, while the Polish-Swedish Union entered the fray on Austria's side, aiming to annex Slovakian lands. A decisive Polish-Swedish victory at the Battle of Petrova in 1757 destroyed the Hungarian army, yet the occupied nation refused to capitulate, leaving Austrian forces tied down.

The conflict expanded into a continental catastrophe in 1759 when Russia and Prussia opportunistically declared war on the Austro-Polish alliance. The Polish-Swedish Union was besieged on two fronts; Prussian troops seized Silesia and parts of Poland, while Russian armies poured into the Ukraine and Lithuania. The Habsburgs suffered a humiliating total defeat against the Prussians at the Battle of Vitkov in 1760, which decimated their army in Slovakia. Simultaneously, the Polish military collapsed following a disastrous engagement against the Russians at Warka, leaving Warsaw defenseless and leading to the occupation of the vast majority of the Commonwealth by Russian and Prussian forces.

Sensing the imminent collapse of its Austrian rival, France entered the war in 1761 to seize the Habsburg Netherlands, an act that triggered Britain’s entry into the conflict per their secret agreement. While France successfully occupied territory in the Low Countries and Franche-Comte, Britain focused on naval and colonial dominance, defeating the French fleet off the Iberian coast and seizing colonies in the Caribbean. The war concluded in 1762 with a reshaping of the European map. The Peace of Reval stripped the Polish-Swedish Union of its Baltic, German, and Ukrainian territories, effectively shattering it as a great power. The subsequent Peace of Potsdam forced Austria to cede the wealthy province of Silesia to Prussia and border lands to France. The Habsburgs emerged from the war defeated and isolated, having failed to pacify Hungary and watching their primary ally be dismantled by the rising powers of the East.