city of strong fortification
It's a metaphor for a city that defends solidly and is not easy to break.
Idioms and allusions
[source]: Chen Shou's biography of Xinpi in the annals of the Three Kingdoms, Wei annals, said: "the art of war says that those who have Shicheng Tangchi with one million armor but no millet can't defend it."
Discrimination of words
We have shichengtangchi, the enemy can't pass.
city of strong fortification
The high and the low are changeable - guì jiàn wú cháng
a scene of desolation after a plague when the population is decimated - shí shì jiǔ kuì
feel responsible for the welfare of the people - jǐ jī jǐ nì