Genghis Khan launches his campaign against the Khwarezmian dynasty in 1219, and requests military aid from their allies and tributaries.

However, despite having aided the Mongols against the Jin dynasty, the Western Xia emperor and his military commander Aša-gambu refuse to take part in the campaign, stating that if Genghis has too few troops to attack Khwarezm, then he has no claim to supreme power.

Infuriated, Genghis swears vengeance and leaves to invade Khwarazm, while Western Xia attempts alliances with the Jin and Song dynasties against the Mongols.

Genghis Khan, receiving no reparations from the Khwarezem Shah, declares war on Persia, consisting at this time of Khwarezm, Transoxiania, and Khorasan.

The Mongol troops approach the walls of Otrar in autumn 1219.

Shortly before, the Mongols had appeared in Kunya Urgench, the capital of the Khwarezmian Empire, where a war council had taken place and where one of the commanders had proposed to open the battle against the Mongols, but Muhammed II has chosen another way, dispersing his troops by garrisons throughout the towns, allowing the commanders to fight singly.

Despite a heroic defense of the city, its fate is sealed.

The town is destroyed and its population massacred and partially enslaved.

The one hundred thousand- to to one hundred and fifty thousand-man Mongol army, looting and destroying all cities that refuse to surrender, spares only artisans and engineers (whom they recruit, eventually taking them back to their tent-capital at Karakorum to help construct their civilization) as it shatters Otrar and …

…Khojend.

After subjugating those cities not totally destroyed by them, the Mongols permit their inhabitants to rebuild and resume trade.

Many of the towns in the oasis never recover and are abandoned.

During the invasion of Transoxania in 1219, along with the main Mongol force, Genghis Khan uses a Chinese specialist catapult unit in battle.

They will be used again in 1220 in Transoxania.

The Chinese may have used the catapults to hurl gunpowder bombs, since they already have them by this time.

While Genghis Khan is conquering Transoxania and Persia, several Chinese who are familiar with gunpowder are serving with Genghis's army.

Historians have suggested that the Mongol invasion brought Chinese gunpowder weapons to Central Asia.

One of these was the huochong, a Chinese mortar.

Nuremberg was probably founded around the turn of the eleventh century, according to the first documentary mention of the city in 1050, as the location of an Imperial castle between the East Franks and the Bavarian March of the Nordgau.

The fortified town receives its charter as a free imperial city in 1219.

Prince Louis, who had returned to France in 1217 to resume a principal role in the Albigensian Crusade, leads another military expedition to southern France in 1219.

The Muslims, seriously alarmed by February 1219, offer peace terms that include the cession of Jerusalem.

King John and many of the crusaders are eager to accept, but Pelagio, supported by the military orders and the Italians, refuses.

William of Holland, after hearing this, leaves the crusade and sails for home.

Quarreling Roman families force Honorius III to flee to Viterbo, Italy, in June 1219; Frederick reconciles the rebellious Romans with the Pope.

Andrew’s foreign policy is a total failure also.

His younger son, Coloman, who had been crowned King of Halych, is expelled from his kingdom in August 1219 by Prince Mstilav of Novgorod.

Andrew has to make peace with the Prince of Novgorod and he also engages his youngest son, Andrew, to one of his opponent's daughters.

Rastko (later canonized as St. Sava), the younger brother of Stefan II Nemanja, Grand Prince of Serbia, counters his brother's affinity to the Roman Catholic church by traveling in 1219 to Nicaea—refuge of the exiled patriarch of Constantinople—where he receives the title of autocephalous archbishop of Serbia.

Emperor Theodore Lascaris has meanwhile strengthened his ties to the Latin empire by taking as his third wife Maria, daughter of the empress Yolanda, and by proposing that Greek and Latin clergy meet in Nicaea to consider the reunion of the two churches.

In August 1219, Theodore makes a lucrative commercial agreement with the Venetians in Constantinople.

Peter II of Courtenay is a son of Peter I of Courtenay (d. 1183), the youngest son of Louis VI of France and his second Queen consort Adélaide de Maurienne.

His mother was Elisabeth de Courtenay, daughter of Renaud de Courtenay (d.1194) and Hawise du Donjon.

Peter had first married Agnes of Nevers, via whom he had obtained the three counties of Nevers, Auxerre, and Tonnerre.

He had taken for his second wife Yolanda of Flanders, a sister of Baldwin and Henry of Flanders, who were afterwards the first and second emperors of the Latin Empire of Constantinople.

Peter had accompanied his cousin, King Philip Augustus, on the crusade of 1190 and fought (alongside his brother Robert) in the Albigensian Crusade in 1209 and 1211, when he took part in the siege of Lavaur.

He was present at the Battle of Bouvines in 1214.

When his brother-in-law, the emperor Henry, died without sons in 1216, Peter had been chosen as his successor, and with a small army had set out from France to take possession of his throne.

Consecrated emperor at Rome, in a church outside the walls, by Pope Honorius III on April 9, 1217, he had borrowed some ships from the Venetians, promising in return to conquer Durazzo for them; failing in this enterprise, he had sought to make his way to Constantinople by land.

On the journey, he had been seized by the despot of Epirus, Theodore Komnenos Doukas, and imprisoned.

Because his fate is unknown (although he was probably killed), Peter’s wife, Yolanda, who pregnant with her tenth child, had succeeded in reaching Constantinople, rules as regent.

Peter and Yolanda’s oldest son, Philip II, Marquis of Namur, refuses the empire and it falls to his next oldest brother brother Robert, who like, Philip, is still in France.

Peter dies, probably by foul means, after an imprisonment of two years, and thus never governs his empire.

Yolanda has meanwhile allied with the Bulgarians against the various successor states of the Eastern Roman Empire, and has been able to make peace with Theodore I Lascaris of the Empire of Nicaea, who marries her daughter, Marie, shortly before Yolanda’s death in September, 1219.