In January 1384, Vytautas promised to cede part of Samogitia to the Teutonic Order, up to the Nevėžis River, in return for recognition as Grand Duke of Lithuania.

Tokhtamysh, Khan of the Golden Horde, sought help from Vytautas when he was removed from the throne in 1395 after his defeat by Timur.

An agreement was reached that Vytautas would help Tokhtamysh to regain power, and the Horde would cede more lands to the Grand Duchy of Lithuania in return.

Continuing attempts on the part of Poland to subordinate Lithuania drove Vytautas for the third time into the arms of the Order, and by the Treaty of Salynas in October 1398, Vytautas, who now styled himself Supremus Dux Lithuaniae, ceded his ancestral province of Samogitia to the knights, formed an alliance with them for the conquest and partition of Pskov and Novgorod the Great.

[10] Inspired by his successful campaign against Timur, Vytautas and Jogaila won support from Pope Boniface IX for organising a crusade against the Mongols.

Vytautas waged a war in 1406–1408 against his son-in-law Vasili I of Moscow and Švitrigaila, a brother of Jogaila who with the support of the Teutonic Order had declared himself grand prince.

A major stand-off between the two armies ended without a battle in the Treaty of Ugra, by which Velikiy Novgorod was granted to Jogaila's brother Lengvenis, and the important city of Pskov to Jogaila's envoy Jerzy Nos, the latter settlement a clear violation of the treaty of Raciąż.

[11][12] The war with Muscovy ended in December 1408, on terms that made further conflict with the Teutonic Order inevitable, despite Hermann II of Celje's attempt to negotiate a solution.

First of all, you made and announced a decision about the land of Samogitia, which is our inheritance and our homeland from the legal succession of the ancestors and elders.

However, the knights ruled Samogitia for only three years, because on 13 March 1401, the Samogitians, supported by Vytautas, rebelled and burned two castles.

In 1404 Peace of Raciąż was signed, which in essence repeated the Treaty of Salynas: Samogitia was transferred to the Teutonic Knights.

The army joined Polish forces and advanced towards the Teutonic headquarters at the castle of Marienburg (present-day Malbork).

Even though the siege of Marienburg was unsuccessful, the Teutonic Knights never regained their strength and from then on posed a reduced threat to Poland-Lithuania.

From now on, Poland-Lithuania began to be regarded in the west as a great power, and Vytautas stood in high favour with the Roman curia.

Samogitia was returned to Lithuania in perpetuity, while the city of Memel (present-day Klaipėda) and surrounding territories stayed with the Order.

Vytautas was granted wide autonomy, but after his death the title and powers of Grand Duke of Lithuania were to be transferred to the king of Poland.

In case Jagiełło died first without an heir, the Polish nobility agreed not to elect a new king without consulting Vytautas.

The unique feature of this union was that the Lithuanian nobility presented their own document: for the first time somebody other than dukes played a role in the state matters.

This union was important culturally as well as politically because it granted Lithuanian Christian nobles the same rights as the Polish szlachta.

The envoys who were transporting documents supporting Vytautas's coronation and proposing an alliance between Lithuania, Hungary and the Teutonic Order were stopped at the Polish-Lithuanian border in the autumn of 1430.

According to the Encyclopædia Britannica Eleventh Edition, Vytautas "was certainly the most imposing personality of his day in Eastern Europe, and his martial valour was combined with statesmanlike foresight."

Under his rule the Grand Duchy of Lithuania gradually became more centralised, as local princes with dynastic ties to the throne were replaced by the governors loyal to Vytautas.

Vytautas was a cousin and childhood friend of Jogaila (Władysław II Jagiełło), who became King of Poland in 1386.

After Anna's death in 1418, Vytautas married her niece Juliana Olshanska, daughter of Ivan Olshanski who outlived him.

[19] Because of the relationship between the two women, the Bishop of Vilnius was unwilling to perform the ceremony without a papal dispensation; however, Jan Kropidło did not have such scruples and married them on 13 November 1418.

[21] In the video game Age of Empires II: Definitive Edition, Vytautas featured as a cavalry hero.

Vytautas is also mentioned in Jonathan Franzen's fictitious novel "The Corrections", which attributes his death in 1430 to Lithuania's gradual downfall as a "global player".