I don't think the mountain ranges were as significant from the distance from their cultural and political cities of influence and the lack of interest in further expansion to an area that was pretty average
mongols were still expanding westward until they hit the carpathians and caucuses, and even sent some expeditionary scouting parties through and found there wasn't enough grass to sustain their horses and the land was too poor and backwards to bother with. One of their scouting parties nearly defeated a European army on its own and the Europeans thought they beat the Mongols for good but it was just a small detatchment
They made it as far west as Bulgaria and the Carpathian mountains, and could have easily continued had it been worth it and had there not been annoying choke-points and bottlenecks and rugged terrain - eventually the Mongols did take Bulgaria, but as I was saying, the mountainous terrain in this region is really what walled them off and led to them being ambushed and defeated at higher rates, and reduced the effectiveness and mobility of their armies.
I mean they became the Yuan dynasty
I don't think the mountain ranges were as significant from the distance from their cultural and political cities of influence and the lack of interest in further expansion to an area that was pretty average
mongols were still expanding westward until they hit the carpathians and caucuses, and even sent some expeditionary scouting parties through and found there wasn't enough grass to sustain their horses and the land was too poor and backwards to bother with. One of their scouting parties nearly defeated a European army on its own and the Europeans thought they beat the Mongols for good but it was just a small detatchment
https://en.wikipedia.org/wiki/Battle_of_Samara_Bend
They made it as far west as Bulgaria and the Carpathian mountains, and could have easily continued had it been worth it and had there not been annoying choke-points and bottlenecks and rugged terrain - eventually the Mongols did take Bulgaria, but as I was saying, the mountainous terrain in this region is really what walled them off and led to them being ambushed and defeated at higher rates, and reduced the effectiveness and mobility of their armies.