Mongolian A and the Alphabet the Mongols Adopted

The traditional Mongolian alphabet was taken up around the founding of the Mongol state in the early thirteenth century, and it was not invented for the purpose. It was borrowed whole from the Old Uyghur alphabet, which the Uyghurs had themselves taken from Sogdian, and Sogdian belongs to the family of scripts descended from the Aramaic abjad. A letter such as a therefore has a pedigree that reaches back through Central Asia to the Near East, by way of merchants, scribes and missionaries rather than by conquest. The traditional account of the moment is a small and human one: a Uyghur scribe in the service of a defeated rival was taken into Mongol service and set to teaching the script, which is a plausible enough story for how a working chancery practice moves from one court to another.

What matters more than the anecdote is what the borrowing cost and what it bought. An alphabet built for one language rarely fits another exactly, and this one did not. Sogdian and Uyghur had no need to distinguish the rounded vowels the way Mongolian does, so Mongolian inherited a shortage of vowel signs it never fully repaired. In exchange it received a cursive, joined, vertical writing with a long documentary tradition behind it, which could be put to work immediately on decrees, letters and seals for an empire that suddenly needed all three.