This hexagram seems a very good and prosperous one, but for Wu it was a time of the biggest hardships he had ever endured. It seemed as if everything worked against him. His father died, allies were difficult to find and difficult to convince, the weather was awful, and on top of all that there were the omens ...
He could only succeed because he had such a tremendous will to fulfill his task. "The king serves it" - a good king is not a boss, he is a servant of his people and of his task.
Wen, lord Chang, the father of Wu, founded his capital at the foot of mount Qi. He was at that time Xibo, Earl of the West, later he would become king Wen. His territory was very small, only a hundred square li, so probably the capital was rather a village. When he was preparing to attack king Zhou of Shang he moved 70 miles Southeast to Feng. Feng was an advance post from where it would be easier to attack the Shang, and excavations show it was rather a military garrison than a city.
The city of Shang, Dayi Shang, was another 380 miles further, to the Northeast.
In Feng, Chang Xibo built a tower, a Lingtai, translated as divine/magic/skyward tower. (língtái: locale of one's spirit; terrace where emperors watched heavenly phenomena).
The Huainanzi suggests he built it for fooling king Zhou into believing he was not interested anymore in serious matters, and no threat for the Shang. But probably it was for searching the skies (sun and stars) for signs, omens which could tell him about favors of gods and spirits, about things bound to happen and about the best course of action. ‘Active all day long, at night apprehensive’ (hex.1.3)
He died before he could attack the Shang, and his son, Wu, had to start the time of mourning: staying away from daily life for three years. This is described in the top line of hex.55.
Wu asked the oracle about mourning, and the oracle said: pitfall. He asked about not mourning, and the oracle said: no mourning, an Yi sacrifice at noon.
At that moment there were omens, mayby sunspots. The third line probably has to do with this: ‘at noon rain-curtains, froth was seen’. Sunspots look as if something is passing in front of the sun. Birds or something else, a curtain of sorts maybe. They can be explained by a bright general as: “the sun is not eaten, a rain-curtain has passed before it, and like on earth, it is a sign of new growth. After the drought of winter, when the rains come, the fields can be worked again, seed can be sown. These "curtains" are a sign of the fall of a dynasty – Shang of course – and a sign of new beginnings”.
I do not know if he said these things of course. Maybe sunspots were explained as crows passing by instead of eating the sun like in an eclipse. Maybe the rain was actually rain and had nothing to do with the omen of the sun.
The Zhou attacked with the help of allies: described in line 1 and 4. In line 1 it is an allied lord, in line 4 one of the barbarians. When Wu set out to conquer Dayi Shang, many ´great princes of friendly states´ joined in the battle. Some of these were befriended with the Zhou, but others joined only for the mutual goal. With a friend one has to consider the borders of what one can demand or tolerate, the contact itself is no problem. If one behaves oneself ´like a friend´: not jumping up at a saying, not reacting with suspicion or disdain, then the friend will stay a friend, even in tough circumstances.
But with a ´barbarian´, where the exchange is tense, one has to restrain oneself, weigh every word carefully, and, if possible, try to find an opening for contact by searching for mutual grounds. Meet him halfway, but without making yourself vulnerable.
Line 4: even those who were usually not friends (the tribe of Yi) came to help, but everyone had to hide his true feelings for the time being (line 4 changes to hex.36)
Line 5: ‘rewards come’, changes to hexagram 49, about revolution, changing the mandate. ‘The great one changes like a tiger, he finds belief (or his truth shows) even before the augury’: for the army, Wu did not need the oracle’s sanctioning, his power of action and expression convinced them. He was like the ´Tiger Braves´, the 3000 men in his army who excelled above all others, and who were trained in battle tactics by Taigong.
But Wu gathered only after the verification of his having the mandate (line 2).
Line 3: At Feng rain-curtains. At noon one sees froth. Breaking one´s right arm, no fault.
The rain-curtains are Pei4, profusion, "Heavy rain, sudden rain; abundant; marsh; N. pr. of a river" –Karlgren (1923).
Marshall p.76: Shi Ji 32 states that King Wu wished to attack King Zhou and performed a tortoise divination, but the results were not auspicious, and violent wind and rain arose as additional bad omens. The assembled dukes were afraid, but Taigong, the king´s commander and military strategist, ´stiffened them to support King Wu´. King Wu then marched on the Shang.
And Marshall p.189, n.36: The Han Shi Wai Zhua also mentions the bad omens of King Wu´s shield breaking in three places and it raining continuously for three days, which Taigong re-interpreted favourably to spur both the king and the troops on to victory.
Wu having his arm broken is also mentioned somewhere, but I could not find that anymore.
Hex.56 is about new or unknown circumstances. New people, a new country, new experiences. When one does not know the habits or facts one might encounter, then one should be extremely modest and careful.
Don't break out a wall in a house you hardly know, don't make jokes in a new job, don't be impulsive toward a stranger, don't criticize people in another country. All these mistakes might cause severe harm.
About losing sheep/cattle at Yi (in hex.34 sheep, in 56 cattle):
Whincup, p.121 (hex.34): This refers to the story of the Shang ancestor King Hai, a story which has been reconstructed from various ancient references (Gu, 1931). King Hai (Wáng Hài) was probably a herdsman who crossed over with his sheep and oxen from his own land to the neighboring territory of Youyi. He lived there happily for several years until he made the mistake of committing a serious crime, perhaps adultery with one of the ruler’s women. His herds were confiscated and he was put to death. He gained his royal title only much later, when his descendants founded the Shang Dynasty.
Kerson Huang: The I Ching most likely had its roots in the divination traditions of the Shang. The Shang people deified their ancestors, to whom periodic offerings were required, with the proper ceremony. These rites were among the most important duties of the king.
Of the early ancestors of the Shang people, only three were considered important enough to merit the title of “High Ancestor”, and they were honored with especially elaborate sacrifices. Among them was Wang Hai (Prince Hai), who figures prominently in the I Ching, though it is not clear why he in particular is referred to so frequently.
Prince Hai (ca. 2000 B.C.) was a clever, enterprising, and restless man who left his home to travel to the Kingdom of Yi to raise cattle and seek his fortune: "Little, little traveler; Courting disaster". There Prince Hai encountered mysterious conspiracies against him. He had a flourishing flock of sheep, but somehow lost it: "He lost his sheep in the Kingdom of Yi. No regrets". (34 Great Vigor)
He then raised oxen and invented the ox yoke to put them to work in the field. There was an attempt to burn him to death in his house, from which he was able to escape only because a mysterious rap on his bed roused him: "Hitting the bed with the foot. The dream bodes ill". (23 Loss)
His luck did not hold out for long, however: The local King, Mianshen, who may have been behind all the conspiracies, finally killed him and took his oxen: "A bird's nest is burning. The traveler first Iaughs then weeps. He loses his oxen at the Kingdom of Yi. Disaster". (56 The traveler or wanderer)
Prince Hai's death was eventually avenged by his son Wei, who, with the assistance of a neighboring state, attacked Yi and killed Mianshen.
A century after Prince Hai, his descendant Lord Tang overthrew the Xia and founded the Shang Dynasty.
This might be partly myth, but since the Yi is not a book of history, but a book of divination, it is not really important wether a diviner illumines his sayings with the images of myth or with historic facts. It only matters if everyone understands what he wants to say.