Although Jiang Xu looks very calm on the outside, no one knows that he was actually very nervous. Before he went here, he had already heard a lot of good things about the emperor, and seeing the emperor up close, he immediately knew why the people of Xiang worship their emperor.
Aside from the good looks of the emperor, the emperor also handles his harem pretty well which is rare for an emperor of a flourishing empire. The emperor also puts his people above anything else, earning the love and praise from the masses. The emperor of Xiang is portrayed as an upright ruler, and what he saw is definitely the same as how the people view their emperor.
Although Jiang Xu is a general, it does not mean that he is not normal like any other people. Although Jiang Xu appears cold, he is not like those cold-blooded general who only thinks of killing. He, himself, had dreamed of having a peaceful and loving family. His family was a great influence to this. Their family was not like any other household. The Jiang family is surprisingly harmonious. Unlike everyone, Jiang Xu did not grew up in a scheming and polygamous family. His father only had him and his mother. Even though his father only had his mother, his grandfather understand their situation.
After all, their family holds a tradition where anyone on their family can only spend their entire lifetime with one person, and Jiang Xu promised to himself that this tradition would not end on his generation.
Regarding his situation, clearly Jiang Xu could wipe out the entire enemy if he was in his perfect condition. But luck was not on his side. The Bei's sent someone to spy and seduce Jiang Xu. Believing that the woman truly loved him, he treated her gently, though he did not reciprocate her feelings. Jiang Xu felt uncomfortable with the woman so he told her to stop pursuing him. She agreed, but he must go out and show her around first. So he agreed, he never thought that he will be schemed by someone- especially a woman who he thought had liked him- so he lowered his guard, and was led by the nose until he almost died. He could not be blamed though. Jiang Xu grew up in the military, and spent his childhood and adulthood in training and preparing for his dreams. Unlike any other young masters, Jiang Xu doesn't have the luxury of going out to brothels to 'explore'. Thus, explaining his naïvety in the matters of love.
As a result of his 'lack of experience', Jiang Xu was poisoned, and was nearly killed by an assassin if it wasn't for his subordinate. He was at the brink of death, when he was found by his subordinate and sent to the physicians to be treated. He was greatly injured, and couldn't completely participate in the war. The Tang emperor was mad, not to him, but to the Bei's for using such under-handed tricks. He was guilty because he knew that as a general he should have been more careful towards the people around him, and he should have investigated her identity first. But he didn't, and he almost killed all the people of Bei for his stupidity.
He knew that if he was more careful from the start, anything related to his injuries wouldn't have happen, so he felt like it was his responsibility. So he went and asked the emperor of Tang's pardon and permission to allow him to go to Xiang to ask for their help. He was allowed to go. He went to Xiang with the mindset to help his people and to correct his mistakes no matter what the costs are.
Thus, they set off from Tang to ask for Xiang's aid in the war with the Bei's.