The Battle of the Talas River is now often called "the most important battle you've never heard of" with the Arab victory supposedly halting further Chinese conquests in Transoxiana, and paving the way for the eventual Islamization of Central Asia. Of course, this (and is acknowledged to have) also relied on the An Lushan Rebellion causing Tang contraction. However, from an AH perspective, would a Chinese victory at the Talas have aborted the An Lushan Rebellion? Because if not, the Arabs suffer a few losses, the Chinese collapse in a few years anyway, and they're let to pick up the pieces as if nothing happened. This, of course, would relegate its importance to a footnote.