Jogaila had sent Klemens Moskarzewski to establish a Polish garrison in Vilnius and stabilize the situation, but this move only angered the opposition.
In May 1389 Jogaila tried to mediate the conflict between Skirgaila and Vytautas in Lublin.
Vytautas was pressured into signing a formal document declaring that he was loyal to Skirgaila and supported him, but his position as Duke of Lutsk was not formally acknowledged.
Vytautas secured his position in Lutsk, and turned his sights on Vilnius.
According to Teutonic testimony at the Council of Constance, Vytautas planned to take advantage of his sister's wedding by sending wagons filled with meat, hay, and other goods to Vilnius.
The wagons would be escorted by armed men, who would capture the castle once inside the city.
This plan was uncovered by a German spy and the conspirators were executed.
In another setback, two of Vytautas' strongest allies, his brother Tautvilas and his brother-in-law Ivan Olshanski, lost their territories in Navahrudak and Halshany.

Vytautas then sought a military alliance with the Knights, sending captive knight Marquard von Salzbach to negotiate.
On 19 January 1390 in Lyck Vytautas signed the Treaty of Lyck affirming the terms of an earlier agreement, the Treaty of Königsberg, signed in 1384 during his first conflict with Jogaila.
Under the terms of this treaty, the Knights were promised Samogitia, up to the Nevėžis River, in exchange for their military assistance.
Having been earlier betrayed, the Knights asked for hostages as a guarantee of Vytautas' loyalty: his brothers Sigismund and Tautvilas, his wife Anna, his daughter Sophia, his sister Rymgajla, his favorite Ivan Olshanski, and a number of other nobles.

In May, a delegation of 31 Samogitian nobles arrived in Königsberg and promised loyalty to Vytautas by signing the Treaty of Königsberg.
The joint forces of Vytautas and the Teutonic Knights consisted largely of volunteers and mercenaries from western Europe, notably from France, the German states, and England.
Henry, Earl of Derby, the future King Henry IV of England and Marshal of France Jean Le Maingre were among the participants.
The English crusaders left detailed records of their actions in Prussia and Lithuania, and their exploits were mentioned by Geoffrey Chaucer in the Canterbury Tales, possibly as a compliment to the English knights and the future king.
In the meantime, Jogaila achieved some military successes; his forces captured several castles in Podlaskie, leaving them to be guarded by Polish garrisons, and took Hrodna in April 1390 after a six-week siege.

The newly assembled coalition organized a number of small campaigns in Lithuania; the largest was undertaken at the end of summer.
During this campaign the Knights burned wooden castles at Kernavė, possibly the first capital of Lithuania, which never recovered from the destruction.
While the army was laying siege to Georgenburg, Grand Master Conrad Zöllner von Rothenstein died.
The coalition decided to abandon this siege and march on Vilnius instead, as such a large army could not easily be re-assembled.
On 11 September 1390, the joint forces launched a five-week siege on the city.
Vilnius' castles were held by Skirgaila, commanding combined Polish, Lithuanian, and Ruthenian troops.
The Knights reduced much of the outer city to ruins and managed to destroy the Crooked Castle, which was never rebuilt.
Vytautas' brother Tautvilas Kęstutaitis and Jogaila's brother Karigaila died during the siege.
The besiegers ran into various difficulties.
Their supplies of gunpowder were dwindling, the weather was deteriorating, the terms of service for some volunteers from western Europe ended, and the Knights needed a new Grand Master.
They decided to return to Prussia.
The siege did not bring an end to the conflict, but it demonstrated an increased dissatisfaction with Jogaila among the regional inhabitants.
Jogaila had sent Klemens Moskarzewski to establish a Polish garrison in Vilnius and stabilize the situation, but this move only angered the opposition. In May 1389 Jogaila tried to mediate the conflict between Skirgaila and Vytautas in Lublin. Vytautas was pressured into signing a formal document declaring that he was loyal to Skirgaila and supported him, but his position as Duke of Lutsk was not formally acknowledged. Vytautas secured his position in Lutsk, and turned his sights on Vilnius. According to Teutonic testimony at the Council of Constance, Vytautas planned to take advantage of his sister's wedding by sending wagons filled with meat, hay, and other goods to Vilnius. The wagons would be escorted by armed men, who would capture the castle once inside the city. This plan was uncovered by a German spy and the conspirators were executed. In another setback, two of Vytautas' strongest allies, his brother Tautvilas and his brother-in-law Ivan Olshanski, lost their territories in Navahrudak and Halshany.
Vytautas then sought a military alliance with the Knights, sending captive knight Marquard von Salzbach to negotiate. On 19 January 1390 in Lyck Vytautas signed the Treaty of Lyck affirming the terms of an earlier agreement, the Treaty of Königsberg, signed in 1384 during his first conflict with Jogaila. Under the terms of this treaty, the Knights were promised Samogitia, up to the Nevėžis River, in exchange for their military assistance. Having been earlier betrayed, the Knights asked for hostages as a guarantee of Vytautas' loyalty: his brothers Sigismund and Tautvilas, his wife Anna, his daughter Sophia, his sister Rymgajla, his favorite Ivan Olshanski, and a number of other nobles.
In May, a delegation of 31 Samogitian nobles arrived in Königsberg and promised loyalty to Vytautas by signing the Treaty of Königsberg. The joint forces of Vytautas and the Teutonic Knights consisted largely of volunteers and mercenaries from western Europe, notably from France, the German states, and England. Henry, Earl of Derby, the future King Henry IV of England and Marshal of France Jean Le Maingre were among the participants. The English crusaders left detailed records of their actions in Prussia and Lithuania, and their exploits were mentioned by Geoffrey Chaucer in the Canterbury Tales, possibly as a compliment to the English knights and the future king. In the meantime, Jogaila achieved some military successes; his forces captured several castles in Podlaskie, leaving them to be guarded by Polish garrisons, and took Hrodna in April 1390 after a six-week siege.
The newly assembled coalition organized a number of small campaigns in Lithuania; the largest was undertaken at the end of summer. During this campaign the Knights burned wooden castles at Kernavė, possibly the first capital of Lithuania, which never recovered from the destruction. While the army was laying siege to Georgenburg, Grand Master Conrad Zöllner von Rothenstein died. The coalition decided to abandon this siege and march on Vilnius instead, as such a large army could not easily be re-assembled. On 11 September 1390, the joint forces launched a five-week siege on the city. Vilnius' castles were held by Skirgaila, commanding combined Polish, Lithuanian, and Ruthenian troops. The Knights reduced much of the outer city to ruins and managed to destroy the Crooked Castle, which was never rebuilt. Vytautas' brother Tautvilas Kęstutaitis and Jogaila's brother Karigaila died during the siege. The besiegers ran into various difficulties. Their supplies of gunpowder were dwindling, the weather was deteriorating, the terms of service for some volunteers from western Europe ended, and the Knights needed a new Grand Master. They decided to return to Prussia. The siege did not bring an end to the conflict, but it demonstrated an increased dissatisfaction with Jogaila among the regional inhabitants.
Lithuanian Civil War (1389–1392)