Kublai, on becoming Great Khan in 1260, repeatedly attempts to get Dai Viet and Champa to acknowledge his suzerainty as hostilities gradually escalate.

The Vietnamese and Chams form an alliance against a Mongol invasion force of an estimated five hundred thousand soldiers, who drive Vietnamese general Tran Hung Dao and his forces south to Tran Hoa.

The Chams, operating from hidden mountain strongholds, wage a strong guerilla campaign.

Ariq Böke, commander of the Mongol homelands, had decided to attempt to make himself Khan, as his older brother Kublai was campaigning against Song China at the time of Möngke's death.

Kublai continues his attack on Wu-han, but soon receives news that his younger brother has held a kurultai at the Mongolian imperial capital of Karakorum and has been pronounced Great Khan.

Most of Genghis Khan's descendants favor Ariq Böke as Great Khan; however, his two brothers Kublai and Hulagu are in opposition.

Kublai quickly reaches a peace agreement with Song troops and returns north to …

…the Mongolian plains, in order to oppose Ariq Böke’s claim to the title of Great Khan.

Upon returning to his own territories, Kublai summons a kurultai of his own, and in April 1260 is proclaimed Great Khan.

Only a small number of the royal family supports Kublai's claims to the title; the small number of attendees nevertheless proclaim him Great Khan.

This subsequently leads to warfare between Kublai and his younger brother, which will result in the eventual destruction of the Mongolian capital at Karakorum.

Kublai sends his envoy Hao Jing to negotiate with Song Dynasty Chancellor Jia Sidao on May 21 after the small force left by Kublai south of the Yangtze River is destroyed by a Chinese army of the Southern Song Dynasty.

Chancellor Jia Sidao imprisons the entire embassy of Kublai.

Kublai is unable to assault the Song due to the civil war with his rival brother Ariq Böke, but he will not forget this slight.

Prosperous Venetian merchants Niccolò Polo and his uncle, Maffeo Polo, partners with a third brother, named Marco il vecchio (the Elder), trade with the East.

In 1252, Niccolò and Maffeo had left Venice for Constantinople, where they had resided for several years.

The two brothers had lived in the Venetian quarter of Constantinople, where they had enjoyed political privileges and tax relief because of their country's role in establishing the Latin Empire in the Fourth Crusade of 1204, but the family had judged the political situation of the city precarious, so they decided to transfer their business northeast to Soldaia, a city in Crimea, and left Constantinople in 1259. (Their decision proves wise, given Constantinople’s recapture two years later by Michael Palaeologus, the ruler of the Empire of Nicaea, who then promptly burns the Venetian quarter. Captured Venetian citizens are blinded, while many of those who manage to escape perish aboard overloaded refugee ships fleeing to other Venetian colonies in the Aegean Sea.)

As their new home on the north rim of the Black Sea, Soldaia had been frequented by Venetian traders since the twelfth century.

The Mongol army had sacked it in 1223, but the city had never been definitively conquered until 1239, when it became a part of the newly formed Mongol state known as the Golden Horde. (Today it is a popular resort, most famous for its Genoese fortress, the best preserved on the northern shore of the Black Sea.)

Searching for better profits, ...

…the Polos had continued their journey to Sarai, where the court of Berke Khan, the ruler of the Blue Horde, is located.

At this time, the city of Sarai—already visited by William of Rubruck a few years earlier—is no more than a huge encampment, and the Polos stay for about a year.

Finally, they decide to avoid Crimea, because of a civil war between Berke and his cousin Hulagu or perhaps because of the bad relationship between Berke Khan and the restored Empire of the Greeks.

Instead, they move further east to Bukhara, where they will remain for three years.

Galicia-Volhynia under Daniil's reign is one of the most powerful states in east central Europe, although it is forced once again to submit to Mongol vassalage in 1260.

Literature flourishes, producing the Galicia-Volhynian Chronicle.

Demographic growth has been enhanced by immigration from the west and the south, including Germans and Armenians.

Commerce has developed due to trade routes linking the Black Sea with Poland, Germany and the Baltic basin.

At the peak of its expansion, the Galicia-Volhynian state contains not only all of southwestern Ruthenia, including Red Ruthenia and Black Ruthenia, but also briefly controls the Brodnici people on the Black Sea.

Major cities, which serve as important economic and cultural centers, include L'vov (where the royal seat will later be moved by Daniil's son), …

…Vladimir-in-Volhynia, …

…Halych, and …

…Terebovl'a.