What could prevent Ming do to so, or at least to make their attempt unsuccessful? Would a Northern Yuan victory in Mongolia directly lead to reconquer parts of Northern China?
The Ming clearly identified the Northern Yuan as a threat and was hellbent on eradicating it, at least during the early parts of the dynasty.In the dynasty's early days,they also have a lot of Mongol auxiliaries in it's service to counter Mongol advantage in cavalry.It really depends on the scale of defeat of the Ming Chinese.I highly doubt it would be easy,given that early Ming was dominated by a lot of highly competent leaders.As for reconquering parts of China,I see it as unlikely considering the amount of resources used towards fortifying the border.The Battle of Tumu showed that even in the highly unlikely event that the emperor's captured and the entire Ming field army got completely wiped out,there's no way the Mongols could have conquered Ming when the economy's still running and the government still held legitimacy.
I do wonder though if the Mongols can exploit the civil war between Jianwen and his uncle Zhu Di (who later became Emperor Yongle).
How do you think it would happen?
Others will have to answer this because it's out of my league.
Timur manages to live long enough to invade china, maybe.
Would weaken the Ming and open the door for a yuan comeback.
Most unlikely.If Timur lived long enough to invade China,he's going to find his head on a pike.He will be invading a land far from his power-base,lead by another military genius(Yongle Emperor) whose army would not only dwarf whatever army he could muster,but can counter his advantage in nomad cavalry by fielding auxiliary Mongolian horsemen.