He who wins is the king;
He who loses is the rebel.

Let’s begin with an overview for anyone who might not be totally familial with what - exactly - the “Mandate of Heaven” really is, as well as where it came from, and its role in Chinese dynastic rulership. Then we’ll get to the main part of your question of when and under what circumstance it did/did not apply, and what was/was not out of the hands of “mere” mortals.

The Chinese Mandate of Heaven is, put most simply, largely analogous to the Western/European concept of Divine Right of Kings. It establishes the current holders of political power – the imperial clan – as having been divinely appointed and empowered to justly rule, nominally at least, the whole earthly world (天下)

The Mandate of Heaven, or Tiānmìng (天命), came about in the course of an epochal shift in power dynamics across the Yellow River Valley. Now, if you go and ask more traditional Chinese historians, they’ll put it more simply – that it was the end of the Shang/Yin Dynasty, which was overthrown and supplanted by the Zhou Dynasty circa 1046 BCE, culminating with the Battle of Mu Fields. The (much) later chronicler of the early Han Dynasty, Sima Qian, would write of the battle in the Shiji from the perspective of the Zhou army facing them:

The Yin-Shang Legions,
Their banners of war arrayed like a forest,
Amassed on the field of Muye.

“Arise, my lords!” [spoke Shang-fu to the King and his men,]
“The Lord on High looks down on you;
Have no second thoughts!”

The fields of Mu were so broad.
The sandalwood chariots gleamed brightly.
The teams of bays, four astride, black-maned and white-bellied, galloped swiftly

There was the Great General Shang-fu,
Riding like an eagle on the wind,
Aiding King Wu
Who at once smote the great host of Shang
Meeting and clashing that morning, clear and bright.

Whether things were actually quite so “Pelannor Fields,” is significantly more up-in-the-air, as many more modern historians have come to understand the Xia/Shang/Zhou periods and transitions of a heroic re-writing of a multi-civilizational power-dynamic shift, than the linear progression of one dynasty to the next in (what would become) the “typical” Chinese fashion. But that’s neither here nor there for our purposes here…

The ascendant King Wu of Zhou who won the Battle of Muye, however, would die before finishing his foe off complete – which left the task to his son, King Cheng, to consolidate their holdings. This led to a triumvirate, which then devolved into a civil war between Song and his uncle Duke Dan, which ended in a standing down of hostilities on all sides and them agreeing that they needed a peaceful means by which to affirm both their lines legitimacy of rule and the line of succession moving forward.

In the aftermath of the civil war’s denouement, the question still remained as to exactly how the still-shake tripartite government of the nascent Zhou would move forward. The King’s two top advisers, Duke Wen of Zhou and his half-brother Duke Kang of Shao, had markedly differing ideas of how a ruler derived and maintained the legitimate right to governance. The Duke of Zhou argued, in effect, for a meritocracy – questioniong the willing and efficacy of Heaven in deciding earthy rulers and coming to the conclusion that “Heaven helps those who help themselves.” Whatwas more, Zhou put it that Heaven had conferred its mandate onto the people as a whole, stating, “If there were not these [capable and moral men,] able to come and god to conduct the fine teaching, King Wen would have had no virtue to send down upon the men of the state. By acting to make know Heaven’s awesomeness, it was these [men] who made King Wen enlightened; by acting to make [him] visible and striving to me [him] audible to [The Sovereign] on High, it was also these [men] who had received the mandeate of the Yin.”

The Duke of Shao, on the other hand, countered that is was the king and the king alone, as the “eldest son” of Heaven, who had received the divine mandate of rule. “August Heaven, [Sovereign] on High, has changed the eldest son and the mandate of the great state of Yin. It is the king who has received the mandate.” The king alone held the unique virtue, he continued, of being able to consult with Heaven itself – as well as his advisers, of course – since as he is the “son,” so is Heaven his “father.” And while granting Zhou that indeed all men have a hand in shaping their own destiny, they were likewise born with unique virtues and qualities that were immutable. Thus, a true king is unique among men, and one one born such as he is capable of true Virtue:

“Heark! It is like giving birth to a son: there is nothing that is not in the initial birth; he himself is bequeathed his wisdom and his mandate. Now Heaven will command wisdom, command fortune, and command a set number of years. Knowing that now we have for the first time undertaken to inhabit this new city [Fenghao], may it be that the king quickly respects his virtue.”

With his uncles so divided, it would fall to King Cheng himself to break the stalemate – and surprise, surprise, he sided with Shao telling him that he was Superman, rather than Zhou telling him he was first among equals. Nevertheless, it would be a debate hashed out again and again for the subsequent 3,000 years – between the ruler of the era and his ministers, between religion and the state and the place of both in the other’s affairs, and in truth has never been satisfactorily resolved. The concept of the Mandate of Heaven was created to justify a rebellion, but then also to sustain and empower the subsequent dynasty – that very tension at its heart, that dual purpose – of legitimizer and overthrower – has stuck with it across time, and makes it very difficult to pin down. Nevertheless, let’s try…

The early rulers of Zhou would build off of the philosophy of King Cheng’s ancestor, the pre-dynastic ruler of the Wen River Valley who would later by restyled as King Wen of Zhou. King Wen had been the ruler who had initially raised the flags of rebellion against the Shang kings, who he (and many others across the realm) had determined had become immoral and selfish rulers, unfit to rule. Central to that ideology was the concept of 文 (Wén) – a term which is deceptively simple in form, but complex in meaning. Most succinctly, it can be translated as “civility and culture” – and is the polar-opposite of its binary counterpart, 武（wǔ), “martial and warlike.” Yet far from being ideas that stood in opposition to one another, they – like much of Chinese cosmology sought a homeostatic and fluid balance between them. From Liu Xiang’s Shuoyuan, “King Cheng enfeoffed Bo Qin [the Duke of Zhou's son] as the Duke of Lu. Summoning him, he addressed him, saying:

"Do you know the Way of acting as the ruler over the people? ... Should you possess the civil [Wen] but lack the martial [Wu], you will have no means to awe those below. Should you possess the martial but lack the civil, the people will fear you but not draw close. If the civil and martial are implemented together, then your awe-inspiring virtue will be achieved."

The entanglement of the Mandate with the concept of Wen is important because it attaches a whole suite of stipulations and requirements that must be met (or broken) to determine whether the Mandate is being upheld by the ruler toward the people. The Mandate of Heaven, though conferring absolute political legitimacy, is not itself absolute in nature. It can be lost (as demonstrated by the overthrow of the final Shang kings) should the cease to follow the righteous path of virtue. As Mencius would put it, “Heaven did not create the people for the sake of the ruler; rather, Heaven created the ruler for the sake of the people” … or somewhat more contemporarily, in the words of Uncle Ben Parker, “With great power comes great responsibility.”

The Duke of Zhou would lay out the conditions by which the Mandate could be staid to have been lost (and thereby conferred on another, worthier candidate in his Announcement of Shao:

Ah! August Heaven, High God, has changed his principal son and has revoked the Mandate of this great state of Shang. When a king receives the Mandate, without limit is the anxiety of it. Ah! How can he fail to be reverently careful!

Heaven has rejected and ended the Mandate of this great state of Shang. Thus, although Shang has many former wise kings in Heaven, when their successor kings and successor people undertook their Mandate, in the end wise and good men lived in misery…The king should have reverent care of his virtue.

Look at the former peoples of ancient times, the Xia. Heaven guided, indulged, and cherished them, so that they would strive to understand what Heaven favors, but by this time they have let their Mandate fall to the ground. Now look at the Shang; Heaven guided them, stayed near them, nourished them, so that they would strive to comprehend what Heaven favors; but now they have let their Mandate fall to the ground.
Now a young son succeeds to the throne; let him not, then, neglect the aged and experienced. Not only do they comprehend the virtue of our men of old - nay, more, they are sometimes able to comprehend counsels that come from Heaven. Ah! Even though it be that the king is young, he is Heaven’s principal son. Let him be grandly able to be in harmony with the little people.

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