Refers to the political treatment given to Cao Cao by Emperor Xian of Han Dynasty in the 23rd year of Jian 'an.
"Praise the unknown" means that you appear before the emperor, and the master of ceremonies only reports the official title and does not call you by your first name. "Don't rush into the DPRK" means that you don't have to take small steps to show your respect when you meet the son of heaven. "The sword goes to the temple", that is, when it appears in front of the emperor, you can wear weapons and shoes. "Like the story of Xiao He" means enjoying the treatment that Liu Bang gave Xiao He.