When his first attempt to take the capital city of Vilnius failed, Vytautas forged an alliance with the Teutonic Knights, their common enemy – just as both cousins had done during the Lithuanian Civil War between 1381 and 1384.

The family of Gediminas ruled a state that covered the territories of present-day Lithuania, Belarus, Ukraine, Transnistria, and parts of Poland and Russia.

Gediminas died in 1341; afterwards his sons Algirdas and Kęstutis, the fathers of Jogaila and Vytautas, co-ruled the Grand Duchy peacefully.

[1] As a condition to the marriage and coronation, Jogaila agreed to renounce paganism himself and Christianize his subjects, and establish a personal union between Poland and Lithuania.

[2] Thus the Order sought opportunities to undo the Polish–Lithuanian union; they demanded Samogitia, a section of western Lithuania that bordered the Baltic Sea,[3] and refused to recognize Jogaila's baptism in 1386.

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.

[3] 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.

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.

[10] 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.

[15] 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.

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.

[20] The Teutonic Knights were idled during the protracted selection of their new Grand Master, Konrad von Wallenrode; their general chapter delayed his election.

[19] In May 1391, the new master mortgaged Złotoria (Slatoria), a castle near Thorn, from Władysław Opolczyk, count palatine of Sigismund of Hungary, for 6,632 guldens.

[6] In November 1391 Vytautas attacked the areas near Merkinė and Hrodna, cutting off the easiest communication route between Jogaila and Skirgaila.

[25] Neither Jogaila nor Vytautas had gained a clear advantage and the territories of the Grand Duchy affected by the civil war were being devastated.

[5] Polish nobles were dissatisfied with the war; Jogaila was spending a great deal of time on Lithuanian matters and the expected benefits of the Union of Krewo had not materialized.

[9][25] Since this agreement with Jogaila was reached in secret, the Knights suspected nothing when Vytautas invited them to the festivities at his headquarters, the Ritterswerder Castle on an island in the Neman River.

[30] Vytautas ruled Lithuania until his death in 1430; his relationship with Jogaila during these years is sometimes likened to the peaceful power-sharing demonstrated by their fathers Algirdas and Kęstutis.

The Treaty of Salynas was signed in 1398, leaving Samogitia to the Knights, to quiet the Duchy's western front while Vytautas was organizing a major campaign against the Golden Horde.