Initially, he supported the efforts of Andrew III of Hungary, but later turned against him, and became the guardian and the most ardent domestic partisan of the young pretender Charles.

Ugrin III was born into the Újlak (or Ilok) branch of the powerful and prestigious gens (clan) Csák, as the son of Pós (or Pous), who served as Ban of Severin and Master of the treasury in 1235.

The document, issued by Judge royal Andrew, son of Serafin on 20 December 1240, confirms that Ugrin was born sometime in the 1230s and had at least one unidentified brother, whose name and fate is unknown.

[2] Despite Ugrin has lived at least seventy years, he had only one known son from his much younger unidentified wife, Nicholas, whose career rose to its peak during the early reign of Louis I of Hungary and died in 1359 or 1360.

As historian Péter Galambosi considers, Ugrin was made ban by Duke Stephen, but later joined the allegiance of Béla, who confirmed him in that position.

[9] Despite the rapid "changes of government" between the Kőszegis and their rival, the Trencsén branch of the Csáks, in the subsequent months, Ugrin retained his positions for a year, until the autumn of 1273, which reflected the relative insignificance of his political influence and court dignity in that time.

[14] These high-ranking positions show that Ugrin's influence gradually increased within the baronial group, becoming its third most important leader after his relatives, brothers Matthew II and Peter I Csák.

[17] When Ladislaus IV imprisoned papal legate Philip of Fermo in late 1279, Ugrin lost his dignity during a major change in the composition of the royal council.

[18] Based on some indirect data in the contemporary documents, it is plausible that Ugrin became disgraced in the royal court for the remaining part of the reign of Ladislaus.

This includes that the king's mother, Queen Dowager Elizabeth the Cuman was created Duchess of Macsó and Bosnia in 1279, which seriously violated and threatened the local interests of Ugrin.

[20] He built his residence, Újlak Castle (Croatian: Ilok) in Valkó County in the 1280s, after obtained the lordship from his distant relative Dominic Csák under unknown circumstances.

[3] According to a royal charter issued by Andrew III in July 1298, Ugrin and his familiares crossed the river Sava and defeated an invading Tatar army, who had plundered the region of Macsó.

It is possible the army was hired by Bulgarian warlords Darman and Kudelin against Stephen Dragutin's realm, who ruled the neighboring Hungarian banates and northern Serbia, altogether known as Lower Syrmia.

[23] In the latter year, Andrew sent Ugrin to Primorje in order to escort his mother Tomasina Morosini to Hungary, but he was captured and imprisoned by certain "disloyal barons".

Under this situation, Ugrin's territory functioned as a buffer zone between the royal lands and Slavonia, where the majority of lords accepted Charles' suzerainty.

[23] Andrew III made his maternal uncle, Albertino Morosini, Duke of Slavonia, in July 1299, stirring up the Slavonian and Croatian noblemen to revolt.

A powerful Croatian baron, Paul Šubić, sent his brother, George, to Italy in early 1300 to convince Charles II of Naples to send his grandson to Hungary to claim the throne in person.

It is possible that Ugrin turned against Andrew already in 1298, as he did not countersign the decrees of the national diet in that year, which aimed to destroy forts built without permission and ordered the punishment of those who had seized landed property with force.

A civil war between various claimants to the throne – Charles of Anjou, Wenceslaus of Bohemia, and Otto of Bavaria – followed Andrew's death and lasted for seven years.

Among them, Ugrin's distant relative, Matthew III Csák dominated the northwestern parts of Hungary (which now form the western territories of present-day Slovakia), Amadeus Aba controlled the northeastern lands, the Kőszegis ruled Transdanubia, James Borsa dominated Tiszántúl, and Ladislaus Kán governed Transylvania, while Paul Šubić ruled over Littoral Croatia and Bosnia as a de facto king.

[29] Following Andrew's death, Ugrin had an important role in the subsequent events; under his guidance, Charles hurried Székesfehérvár, then Esztergom, where he was crowned king irregularly in the spring of 1301.

Through his diplomat Benedict, he also played a decisive role in the concluding alliance between Charles and his cousin Rudolph III of Austria, in Pressburg on 24 August 1304.

[32] According to the Chronicon Posoniense, Ladislaus Kán handed over his prisoner, the self-declared claimant Otto of Bavaria sometimes in the second half of 1307 in Szeged to Ugrin, who "expelled" Charles' last rival pretender from Hungary.

In the same year, Vincent, Archbishop of Kalocsa withdrew the punishment of excommunication against Peter Monoszló, Bishop of Transylvania at the request of Charles and Ugrin Csák.

Gyula Kristó considered the dignity of Master of the treasury elevated into its highest status because of Ugrin's privileged position in the inner circle of Charles.

[38] Ugrin Csák dominated the southern part of the Kingdom of Hungary, acquiring suzerainty over Upper Syrmia and other territories along the river Sava.

[42] When Albertino Morosini left Hungary shortly after Andrew III's death, Ugrin marched into Požega County and captured his duchy.

[43] His biographer, Péter Galambosi doubted Engel's theory that the counties to the east of Syrmia (Keve, Krassó and Temes) belonged to Ugrin's province.

[49] The renowned military leader, Paul Garai initially also belonged to Ugrin's household; he served as castellan of Požega Castle, when it was granted to the arriving Charles.

[51] Ugrin Csák died by the end of 1311; his son Nicholas confirmed one of his former land donations in Požega County on 27 December 1317 and noted the act occurred in the sixth year after his father's death.