The difference between Situ, Sikong and Sima in the beginning?

Situ

The name of the central official is in charge of the land and the people of the whole country.

Sikong

The name of the central official is in charge of the national water conservancy and civil engineering projects.

Sima

The head of the military administration of the state and the principal official of the organs of power.

The first Situ and Sikong existed in the era of Yao Shunyu. For example, Situ --- deeds, respected the Five Religions, treated people with generosity, and finally the people were kind, and Sikong --- Boyu (that is, Xia Yu), which was the matter of Dayu's governance of water. By the time the Zhou Dynasty was founded, Situ, Sikong, and Sima all had them.

In the ninth year, King Wu sacrificed to Yu Bi. Dongguan Bing, as for Mengjin. For king Wen wood lord, carrying a car, the Chinese army. King Wu claimed to be crown prince, and he did not dare to specialize in himself. It is to say to Sima and Situ, Sikong, and Zhujie: "Qi Li, believe in It! To be ignorant, to the ancestors have virtue, and the children are rewarded and punished, so as to determine their merits. "Suixing Division." Shi Shang's father said: "The general Er Zhongshu, and Er Zhou, and the latter are beheaded." "The king of Wu crossed the river, in the middle of the stream, the white fish jumped into the king's boat, and the king of Wu bowed down to sacrifice." As for the royal house, the flow is black, its color is red, and its sound is cloudy. At that time, the princes unexpectedly met with the eight hundred princes. All the princes knew: "The silk can be cut down." King Wu said, "The female does not know the Mandate of Heaven, but she is not yet able to do it." "It is the return of the teacher."