It's not like the entire root of the Ministry of War has rotted, but as far as the "Ma San Case" is concerned, it's highly likely that the Ministry of War has been the secret hand helping the Barbarian Race recover its primordial qi for years. Who can guarantee that this secret hand won't switch sides when the war breaks out?
No need for much, just quietly open Zhuo Huo Pass in the middle of the night and let the Barbarians in—that alone is enough to give the whole Jingjiu Dynasty a taste of disaster.
But it's impossible to sit on the information and not report it—this is a matter of duty, can't be avoided because of fear.
