Jiang Li's statement meant that somebody out there, a hexer or a witch with unparalleled wickedness and evil magic, did something to the millions of soldiers belonging to the Marshal.
They would die once Jiang Li dies. And once it happens, how would Zhao Empire survive?
The soldiers stationed at the South had long viewed Chen Wang as their king. Forget about submitting to a new general the new Emperor would appoint, it would already be a miracle if they did not revolt once they learned that the new Emperor cut off their general's head, no matter if it was for a true rebellion or a frame-up.
A country with no military might would end up gobbled up and trampled down by the surrounding nations because they had nobody to defend them.