One of the earliest forced segregations of…

Much of the Grand Canal south of the Yellow River had been ruined for several years after 1128, when Du Chong decided to break the dikes and dams holding back the waters of the Yellow River in order to decimate the oncoming Jurchen invaders during the Jin–Song wars.

The Jurchen Jin dynasty continually battled with the Song in the region between the Huai River and the Yellow River; this warfare led to the dilapidation of the canal until the Mongols invaded in the thirteenth century and began necessary repairs.

Under the Mongol Yuan dynasty, the capital of China has been moved to Beijing, eliminating the need for the canal arm flowing west to Kaifeng or Luoyang.

A summit section is dug across the foothills of the Shandong massif during the 1280s, shortening the overall length by as much as seven hundred kilometers (making the total length about eighteen hundred kilometers) and linking Beijing and …

…Hangzhou with a direct north-south waterway for the first time.

The Sudovians and Lithuanian invade Samland in 1280, but the Order of the Teutonic Knights, alerted to the danger, has fortified their castles and deprives the raiders of provisions.

Komtur Ulrich Bayer of Tapiau leads a devastating counter-raid into Sudovia while the pagans are in Samlan.

The Polish prince Leszek the Black, who had assumed the throne of Kraków in 1279, achieves two significant victories over the pagans, securing the Polish border, and Skalmantas flees Sudovia to Lithuania.

Magnus, whose birth year has never been confirmed in modern times, was probably the second son of Birger Jarl (Birger Magnuson, 1200–66) and Ingeborg, herself the sister of the childless King Eric XI and daughter of King Eric X.

His father had designated Magnus as his successor in powers of the Jarl, henceforward titled Duke of Sweden.

The (probably) elder brother, Valdemar, had become king succeeding their maternal uncle in 1250.

Duke Magnus, with Danish help, had started a rebellion against his brother in 1275 and ousted him from the throne.

He was elected king at the Stones of Mora.

Magnus in 1276 had allegedly married a second wife Helwig, daughter of Gerard I of Holstein.

Through her mother, Elizabeth of Mecklenburg, Helwig is a descendant of Christina, the putative daughter of King Sverker II.

A papal annulment of Magnus' alleged first marriage and a dispensation for the second (necessary because of consanguinity) would be issued ten years later, in 1286.

Haelwig will later act as regent, probably 1290–1302 and 1320–1327.

The deposed King Valdemar had managed, with Danish help in turn, to regain provinces in Gothenland, the southern part of the kingdom, and Magnus had had to recognize that fact in 1277.

However, Magnus had regained them about 1278 and assumed the additional title rex Gothorum, King of the Goths, starting the tradition of "King of the Swedes and the Goths".

Magnus establishes a Swedish nobility in 1280 by enacting a law accepting a contribution of a cavalry-member in lieu of ordinary tax payments.

Przemysl II had begun to claim his own separated Duchy in 1273, after the victorious expedition against Brandenburg.

Boleslaw V, unable to faced the powerful pressure, had agreed to this and given his nephew the district of Poznań.

To bind Przemysl II with his politics, Boleslaw had arranged the marriage of his nephew with Ludgarda, daughter of Henry I the Pilgrim, Lord of Mecklenburg.

In addition, Ludgarda is a granddaughter of Duke Barnim I of Pomerania, and thanks to this union the alliance with Western Pomerania is reinforced.

However, Przemysł II had soon become involved with Henry IV Probus, and Boleslaw, using the imprisonment of Henry IV in 1277, had tried to force financial concessions, supporting this policy with the marriage of his firstborn daughter Elisabeth with Henry V the Fat, Duke of Legnica.

Boleslaw dies on April 14, 1279, in Kalisz and is buried in the Archcathedral Basilica of St. Peter and St. Paul in Poznań.

Ivaylo nevertheless defeats a larger imperial relief force in the battle of Devina and another numbering five thousand in the Balkan passes.

Despairing of relief, Ivan Asen III flees Tarnovo in 1280, while his brother-in-law George Terter I seizes the throne.

The new ruler temporarily unites the factious aristocracy, and Ivaylo gradually loses support.

He travels in 1280 or 1281 to the Mongol chieftain Nogai Khan, accepting his overlordship and seeking his support to recover his throne.

Nogai is simultaneously approached by Ivaylo's rival Ivan Asen III, who is seeking his own restoration.

Eventually Nogai has Ivaylo murdered, preferring the claim of Ivan Asen III, who is his brother-in-law (both Nogai and Ivan Asen III are married to daughters of Emperor Michael VIII.

Bulgaria is beset by Cuman attacks from the north and by internal upheavals brought on by the growing tax burdens placed on the peasantry by the powerful nobles.

The great peasant revolt of 1277-80 briefly allows the swineherd Ivailo to occupy the royal throne at Turnovo before he is defeated with the aid of Constantinople.

Te Greek Emperor Michael VIII Palaiologos, searing the rapid success of Ivailo, had summoned Ivan Asen to his court, granted him the title of despotēs, and married him to his eldest daughter Irene Palaiologina in 1277 or 1278.

Michael VIII had then sent several imperial armies to attempt to assert Ivan Asen III on the throne of Bulgaria.

Although Ivailo had defeated several of these attempts, he was blockaded for three months in Drăstăr (Silistra) by the Mongol allies of Michael VIII.

In the interval, an imperial force had besieged the Bulgarian capital, Turnovo and, hearing a rumor of Ivailo's death in battle, the local nobility had surrendered and accepted Ivan Asen III as emperor in 1279.

To strengthen his position in Tarnovo, Ivan Asen III marries his sister Maria (Kira Maria) to the Bulgaro-Cuman nobleman George Terter, but fails to assert himself throughout the country.

Ivailo reappears before the walls of the capital and defeats two imperial attempts to relieve Ivan Asen III.

Despairing of success, Ivan Asen III and Irene Palaiologina secretly flee Tarnovo with choice treasures from the palace treasury, including pieces captured from defeated Emperors in former victories.

Reaching Mesembria (Nesebăr), …

…the imperial couple sail for Constantinople, where the enraged Michael VIII refuses to receive them for days for their cowardice.

In 1280 or 1281 Ivan Asen III travels to the Golden Horde, competing with Ivailo in a bid to win support for restoration in Bulgaria.

The Mongol chieftain Nogai Khan eventually has Ivailo murdered, but failed to restore Ivan Asen III in Bulgaria.

The latter returns to his family possessions in the Troad, where he will die in 1303.

The Asen dynasty will be followed by two others, both of Cuman origin, neither of which will succeed in restoring central authority.

Whatever sins Michael VIII may have committed in the eyes of the Orthodox Church, it is true that, by concentrating on the danger from the West, he has neglected, if he has not betrayed, the eastern provinces where he had come to power.

Syrian scholar al-Hassan-al-Rammah, composes, in about 1280, “The Book of Fighting on Horseback and With War Engines,” in which he gives instructions for making gunpowder and rockets, which he calls "Chinese arrows."

Born in Syria, al-Rammah is the first Muslim chemist to successfully create and engineer modern explosives.

He includes one hundred and seven gunpowder recipes, improving upon the gunpowder that had been invented in China.

The first Muslim to invent explosive rockets, he also works on torpedoes and makes several contributions to their design and manufacture.

The governor of Damascus, Sungur, does not agree with Qalawun's ascent to power and declares himself sultan.

Sungur's claim of leadership, however, is repelled in 1280, when Qalawun defeats him in battle.