Yassa

The Yassa was the oral law code of the Mongols, built up gradually through the reign of Genghis Khan and generally understood to have been formally proclaimed at the kurultai of 1206, the great assembly at which Genghis Khan took his title. His adopted son Shigi Qutuqu supervised its compilation and served as the empire's chief judge, while Genghis Khan's second son Chagatai was given responsibility for its enforcement. It grew out of military decrees that were progressively codified and expanded to cover cultural and lifestyle conventions as well as military discipline, property distribution and judicial proceedings, and it was deliberately kept secret, a practice that let Mongol officials modify and apply its provisions selectively. No original Mongolian text of the Yassa survives: what is known of its contents has been pieced together from secondary sources such as the Secret History of the Mongols and the chronicles of contemporaries like Ata-Malik Juvayni, so modern knowledge of its actual provisions remains fragmentary and uncertain compared with better-documented ancient law codes.