In "The Story of Civilization: Our Oriental Heritage", Will Durant makes a passing comment about Genghis Khan's attempt to change the Chinese script to an alphabet-based system.
Is much known about his attempt, and why it failed?
Were other attempts made by others, and what were the circumstances?
Edit: I mistaken refer to Genghis Khan, whereas it should have referred to Kublai Khan. Unfortunately, I cannot edit the title.
OP - are you perhaps getting your wires crossed?
There was a Uyghur scribe employed by Genghis to adapt the Semitic-based Uyghur alphabetic script for Mongolian and an adapted version of it is still in use in Mongolia today, alongside Latin and Cyrillic based scripts, but I'm not aware of any systematic attempt to render Cantonese or Mandarin in to an alphabetic script until the reign of Kublai Khan.
Are you sure you haven't mistaken Kublai for Genghis or Mongolian for Mandarin or Cantonese?