The most powerful Zetan family, the Balšićs, had became sovereigns of Zeta after the collapse of the Serbian Empire in the second half of the fourteenth century.

The province had been annexed to the Serbian Despotate after the death of Balša III in 1421, but after 1455 another noble family from Zeta, the Crnojevićs, become sovereign rulers of the country.

After the disappearance of Gojčin Crnojević from political life in 1451, his brother Stefan had taken over the leadership of the house of Crnojević and become the ruler of a large part of Zeta.

To strengthen his position, he decided to immediately seek foreign protection.

Allying himself with Venice and recognizing its authority over the region, he had subsequently been entitled Duke of Upper Zeta in 1452.

The reasons for the alliance are related to Stefan’s anticipation of the downfall of the Serbian Despot.

Venetan doge Francesco Foscari writes a letter to Stefan in 1455 asking him to return to Budva its territory he had captured.

The near-simultaneous Ottoman invasion of Serbia and conquest of all of its territories south of the Western Morava river completely cuts Zeta off from the core of the Despotate.

Therefore, Duke Stefan Crnojević, together with representatives from all fifty-one municipalities from Upper Zeta, sign an agreement the same year with the Venetians in Vranjina, by which Upper Zeta accepts Venetian rule.

Venice will rule only the cities, while all internal affairs are left to duke Stefan.

The Republic of Venice also binds itself not to meddle in any way with the ecclesiastical authority of the Serbian Orthodox Metropolitan of Zeta.