Ostrów Agreement

The Ostrów or Astrava Agreement (Lithuanian: Astravos sutartis, Belarusian: Востраўскае пагадненне, Polish: Ugoda w Ostrowie) was a treaty between Jogaila (Władysław II Jagiełło), King of Poland and Grand Duke of Lithuania, and his cousin Vytautas the Great, signed on 4 August 1392.

Their joint armies made frequent incursions into Lithuania; the largest attack was launched in the early fall of 1390 when Vilnius was besieged for five weeks.

[3] Polish nobles were dissatisfied that Jogaila spent so much attention on Lithuanian matters and that the Union of Krewo did not bring the expected results.

[4] The negotiations were started in the Ritterswerder Castle on an island the Neman River near Kaunas, where Vytautas resided at the time.

[5] The quick marriage of a Catholic official (though he had not received the Holy Orders of priesthood)[6] and his sudden death within a year were scandalous and sparked many rumors and speculations.

For example, his wife Anna was freed so that she could travel to Lithuania and spread pro-Lithuanian rumors and convert remaining pagans; many nobles were asked to take part in military campaigns.

He spread false rumors that the army of Jogaila and Skirgaila was moving towards Hrodna and organized his forces for a campaign against them.

[4] However, instead of marching to Hrodna, Vytautas attacked Ritterswerder and two other understaffed Teutonic castles on the Neman River before returning to Vilnius.

[4] Simon Grunau spread a false rumor that Iwan and Georg, two young sons of Vytautas, were poisoned by a knight to revenge their father for the betrayal.

[17] Grand Master Konrad von Jungingen led crusaders to Kaunas and then south along the Neman River to Merkinė.

One body of the invaders was left to plunder the countryside and secure route of retreat, another marched about sixty miles east of Hrodna, and the main force reached Navahrudak deep inside Lithuania.

The Knights contemplated expedition against the Victual Brothers in Gotland as their piratical activities interfered with trade of the Hanseatic League.