1251

• The Mongols invade Tibet, but in the process Kublai Khan is converted to Lamaism by the abbot of the Sakya lamasery, whom he then installs as Priest-King of Tibet. The Sakya abbots would rule Tibet in the name of the Mongols until 1358.
• Andrei II, Grand Duke of Russia, is deposed by his his younger brother Alexander Nevsky after he falls out with the Mongols over tribute payments and loses their support.

These people were born in 1251:

• Hojo Tokimune, eigth regent of the Kamakura shogunate.

These people died in 1251:

• Tibetan monk Kanga Gyaltsen, author of the earliest known history of Tibet.

1250 - 1251 - 1252

13th century

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