During the High Middle Ages, the Kingdom of Sweden had expanded across the Baltic Sea and conquered the entirety of what is now Finland (referred to by the Swedes as Österland), and thereby came into contact with the Republic of Novgorod.

From 1471 it was ruled by a regent (Swedish: riksföreståndare), Sten Sture the Elder and was de facto independent, but theoretically it was still part of the Union, a large proportion of its political class favoured close ties with Denmark-Norway.

In 1493, King Hans attempted to put further pressure on Sten by concluding an alliance with Grand Prince Ivan, promising that if he managed to take control of Sweden he would restore the Russo-Swedish border to the line stipulated by the Treaty of Nöteborg.

In late 1495, Ivan sent Princes Daniil Shchenya and Vasily Shuisky to lay siege to the Swedish castle of Viborg, whose commander Knut Jönsson Posse happened to be married to one of Sten Sture's cousins.

These taxes were however very unpopular in Sweden, especially for the Swedish Church, which was already suspicious of Sten for his efforts to encroach upon its traditional freedoms and blamed him for the outbreak of the war with Moscow.

In August a Swedish force under the command of Svante Nilsson sailed across the Gulf of Finland to attack Ivangorod, a castle which Ivan III had built to protect Ingria against the Livonian Order in what is now Estonia and Latvia.

Given Svante's status as the general who had captured Ivangorod, this defection was a major blow to Sten, and in November he was forced to return to Sweden himself to address the gathering unrest against him.