Volhynia had passed into the control of the Lithuanian prince Liubartas after the extinction of the Rurikid dynasty in Galicia–Volhynia in 1323, while the boyars had taken control over Galicia.

They had invited the Polish Prince Boleslaw Yuri II, a grandson of Yuri I, prince of Galicia, to assume the Galician throne.

Boleslaw was born between 1305 and 1310 to Trojden I of Masovia, Duke of Czersk, from the Piast dynasty, and Maria, daughter of Yuri I.

Since his father was still a ruler of the family's Mazovian lands, in 1323 Boleslaw, renamed Jerzy, had become Prince of Galicia.

He also received the Duchy of Belz after the childless death of Andrew of Galicia.

He had in 1331 married the daughter of Grand Duke of Lithuania Gediminas and sister of Aldona of Lithuania, wife of Casimir III of Poland.

Boleslaw Jerzy  in a treaty of 1338 had offered Casimir III of Poland the succession to the throne of Galicia-Volhynia.

Duke Boleslaw is supported by the many German townspeople already living here.

Boleslaw has converted to Orthodoxy and assumed the name Yuri II.

Nevertheless, the boyars, suspecting him of harboring Catholic feelings, poison him in 1340 and elect one of their own, Dmitry Detko, to lead the Galician state.

The kingdom of Galicia will be gradually annexed by the kingdom of Poland between 1340 and 1366, during the reign of Casimir III.

Grand Duke Gediminas of Lithuania, while on his guard against his northern foes, has from 1316 to 1340 aggrandized himself at the expense of the numerous Slavonic principalities in the south and east, whose incessant conflicts with each other have wrought the ruin of them all.

Here, Gediminas’s triumphal progress is irresistible; but the various stages of it are impossible to follow, the sources of its history being few and conflicting, and the date of every salient event exceedingly doubtful.

The grand duchy has in any case greatly expanded it territory, taking control of the rest of the Polatsk principality, as well as …

…the Principality of Turov and Pinsk, and …

…Volhynia.

One of Gedaminas’s most important territorial accretions, the principality of Halych-Volynia, is obtained by the marriage of his son Liubartas with the daughter of the Galician prince.

Königsberg, having become a major trading center, in 1340 joins the Hanseatic League.

It has developed into an important port for the southeastern Baltic region, trading goods throughout Prussia, the Kingdom of Poland, and the Grand Duchy of Lithuania.

The chronicler Peter of Dusburg probably wrote his Chronicon terrae Prussiae in Königsberg from 1324–1330.

Poland’s King Casimir III, reaching an accord with Hungary in 1340, acquires the region of Przemysl from the Rus' kingdom of Galicia-Volhynia, whose own native ruling dynasty had become extinct at the outset of the fourteenth century.

Gedaminas, Grand Duke of Lithuania, has incorporated into his realm the Polish regions of Podlachia and …

…Chelm-Belz.

The imperials had insisted that Nikephoros would be engaged to one of the daughters of the emperor's right-hand man, John Kantakouzenos.

When the time of the engagement came, Nikephoros had vanished.

Andronikos learned that Nikephoros had fled to Italy, with the help of members of the Epirote aristocracy who supported an independent Epirus.

He stayed in Taranto, Italy, in the court of Catherine II of Valois (Philip of Taranto's widow), the titular empress of Constantinople.

A revolt had begun in 1339, supported by Catherine of Valois, who had previously moved to the Peloponnese, and by Nikephoros, who had returned to Epirus, based in Thomokastron.

The imperial army had returned to the area by the end of the year and in the following year, 1340, Andronikos III himself arrives together with John Kantakouzenos.

Nikephoros is persuaded through diplomacy to recognize the authority of the emperor.

He surrenders Thomokastron, marries Maria Kantakouzene, the daughter of John Kantakouzenos, and receives the title of panhypersebastos.