The Treaty of Vienna, concluded on 27 May 1657, was an Austro–Polish

Polish-Lithuanian Commonwealth

The Polish–Lithuanian Commonwealth was a dualistic state of Poland and Lithuania ruled by a common monarch. It was the largest and one of the most populous countries of 16th- and 17th‑century Europe with some and a multi-ethnic population of 11 million at its peak in the early 17th century...

 alliance during the Second Northern War

Second Northern War

The Second Northern War was fought between Sweden and its adversaries the Polish–Lithuanian Commonwealth , Russia , Brandenburg-Prussia , the Habsburg Monarchy and Denmark–Norway...

. After Habsburg emperor Ferdinand III

Ferdinand III, Holy Roman Emperor

Ferdinand III was Holy Roman Emperor from 15 February 1637 until his death, as well as King of Hungary and Croatia, King of Bohemia and Archduke of Austria.-Life:...

 had agreed to enter the war on the anti-Swedish

Swedish Empire

The Swedish Empire refers to the Kingdom of Sweden between 1561 and 1721 . During this time, Sweden was one of the great European powers. In Swedish, the period is called Stormaktstiden, literally meaning "the Great Power Era"...

 side and support the Polish king John II Casimir with 4,000 troops in the ineffective Treaty of Vienna (1656)

Treaty of Vienna (1656)

The treaty of Vienna, concluded on 1 December 1656, was an Austro–Polish alliance during the Second Northern War. Habsburg emperor Ferdinand III agreed to enter the war on the anti-Swedish side and support the Polish king John II Casimir with 4,000 troops...

, his death in April 1657 made way for a more substantial treaty with his successor Leopold I

Leopold I, Holy Roman Emperor

| style="float:right;" | Leopold I was a Holy Roman Emperor, King of Hungary and King of Bohemia. A member of the Habsburg family, he was the second son of Emperor Ferdinand III and his first wife, Maria Anna of Spain. His maternal grandparents were Philip III of Spain and Margaret of Austria...

. By this treaty , Leopold I promised to aid John II Casimir with 12,000 troops against the Swedish-Brandenburgian alliance

Treaty of Labiau

The Treaty of Labiau was a treaty signed between Frederick William I, Elector of Brandenburg and Charles X Gustav of Sweden on 10 November / 20 November 1656 in Labiau...

. These troops were to be maintained at Polish expense, and crossed the Polish border in June.