Attacks from all over
The creation of concrete and bricks was not only useful it was also durable and non-expensive.
The Grand Dowager Empress looked at the slightly warm house and nodded before saying with satisfaction, " This is good. This is really good! If we use these two things then we can rebuild the city walls around the cities that are stated at the borders. This way not only the cities would be protected the constant breaching of the city walls would also stop, what do you have to say, Your Majesty?"
She turned to her son who nodded. He had to admit that Su Wan had really made an incredible service to their imperial family and she indeed deserved a reward.