A Mongol envoy to Korea is murdered here in 1231, prompting Ögödei Khan, Genghis Khan’s son and the second supreme ruler (khakhan) of the Mongol empire, to order an invasion led by General Subutai.

Invading in 1231, Subutai’s forces secure the submission of the larger Korean cities and place Mongol governors in charge.

The mounting opposition to the Ch’oe, Koryo’s ruling military family, increases, causing the fearful puppet-king to flee.

Ögödei is determined to conquer the Henan holdings of the exceedingly rich Jin empire of the Jurzhen, the twelfth-century conquerors of northern China.

Ögödei, his brother Tolui, and General Subutai launch a two-pronged invasion in 1231: Ögödei and Subutai advance from the north and west to form a left wing; Tolui advances from the south with thirty-thousand men to form a left wing.

Tolui’s army meets no opposition until it reaches the mountains, and, although harried there by Jin forces, outmaneuvers them until the Jin withdraw to their capital, Kaifeng, where the remainder of the Mongol forces await.

The Latins, fearing Bulgaria's growing power, repudiate the treaty, and Baldwin is betrothed to the daughter of John of Brienne, titular king of Jerusalem, who is invited to Constantinople to be regent and elected coemperor-regent for life in 1231, thus voiding voiding the regency of John II of Nicaea.

Baldwin is to rule the Asiatic possessions of the empire when he reaches the age of twenty, is to marry John's daughter Marie, and on John's death is to enjoy the full imperial sovereignty.

A large Mongol force, dispatched in 1230 by Khakhan Ögödei to crush the Khwarezmian leader Jalal ad-Din in western Mesopotamia, surrounds him at Diyarbakr in 1231, but their quarry escapes, only to die in Kurdistan later in this year.

Iltutmish builds Sultan Ghari, the first Islamic mausoleum in Delhi, for Prince Nasiru'd-Din Mahmud, his eldest son, in 1231.

The crypt or the tomb is implanted in a Ghari (cave), approached by winding steep stairs made of stone, and supported by pillars and flooring.

The cave is covered by an unusual octagonal roof slab.

The exterior of the tomb structure built in Delhi sandstone with marble adornment exhibits a walled area with bastions (towers) on corners, which impart it the look of a fortress in aesthetic Persian and Oriental architecture.

The imperial marshal, Richard Filangieri, is able to establish himself in Jerusalem and Tyre, which he had regained by treaty in 1229, but not in Beirut or the capital in Acre.

Gregory has responded to the failures of the episcopal inquisition with a series of papal bulls that become the papal inquisition.

The papal inquisition is to be staffed by professionals, trained specifically for the job.

Individuals are chosen from different orders and secular clergy, but primarily they will come from the Dominicans, who are favored for their history of anti-heresy.

As mendicants, they are accustomed to travel.

Unlike the haphazard episcopal methods, the papal inquisition will be thorough and systematic, keeping detailed records.

Some documents from the Middle Ages involving first-person speech by medieval peasants come from papal inquisition records.

The Constitutions of Melfi, promulgated by Frederick II for the Norman kingdom of Sicily in 1231, are Frederick’s outstanding pieces of legislation, part of his efforts to organize the government of Sicily, whose greater freedom he prefers, into unparalleled centralized efficiency.

Mongol hordes besiege the town of Kaifeng, beginning in 1232, but the townsfolk initially repulse them with "arrows of flying fire.” Tied to the shafts are tubes containing an early form of gunpowder, which produces a fiery exhaust.

A contemporary manuscript describes them as "making a noise like thunder" and "traveling a great distance," implying that these first rockets are not purely incendiary devices.

Ivan, thus betrayed by the Empire, hereafter separates the Bulgarian church from Rome.