Short Answer
'Truth' is an idea, and one whose definition is often sanctioned by authority, often without regard for it's correspondence to the state of affairs. Postmodernists often examine the nature of the social aspects of the construction of truth, that is authority-sanctioned claims. For those of us interested in science, both Galileo's tussle with the Catholic church, and Lysenkoism are probably two of the most famous examples of how scientific truth was rejected by political authority for political reasons. Sociologists, who study societies in detail, have a school of thought called social constructionism, which examines how facts, particularly those not about physical reality, come into existence, and are treated by people. This is not only true for kings and presidents, but for logicians, mathematicians, and scientists too!
Long Answer
When people intuitively use truth, they often neglect to understand that such an intuitive use often belies the complexity that the term encompasses. Philosophers come to the table armed with notions such as coherentism, correspondence, and deflationism, among others that show that when the term 'truth' is used, it can be used in different ways by different people for different aims. For instance, when a Catholic priest uses 'truth', he often has a different intention and usage than a scientist. When it comes to political power, again, those who benefit from society, often at the expense of others, use 'truth' differently.
The Catholic Church and Heliocentrism
Science, of course, has from the beginning in its roots of natural philosophy, struggled against dominant political and religious claims of truth. For a long time, the Catholic church, which has existed for thousands of years, maintained political power in Europe, and tortured and executed people who thought differently and made claims counter to religious proclamation. One view that is infamous in science is the geocentric theory of the solar system, and the rival notion called the heliocentric theory. Simply put, the thinkers of the Church maintained that humans were special and the Christian God put the earth at the center of the universe. Giordano Bruno, a Dominican Friar, came to conclusions that clashed with the doctrine of the Church, and was executed. Galileo Galilei somewhat later, had similar problems, but was allotted a much better punishment. It wasn't until Pope John Paul II in 1992 that the Church seemed to come in line conceding its mistake:
Thanks to his intuition as a brilliant physicist and by relying on different arguments, Galileo, who practically invented the experimental method, understood why only the sun could function as the centre of the world, as it was then known, that is to say, as a planetary system. The error of the theologians of the time, when they maintained the centrality of the Earth, was to think that our understanding of the physical world's structure was, in some way, imposed by the literal sense of Sacred Scripture....
— Pope John Paul II, L'Osservatore Romano N. 44 (1264) – November 4, 1992
Soviet Union and Lysenkoism
A 20th century version of scientific truth being 'declared' as opposed to arrived at by scientific practices occurred in the former Soviet Union. While the theory of natural selection put forward by Charles Darwin met (and often still meets) stiff religious resistance as truth, the political elite backed the claims of a man by the name of Trofim Lysenko in regards to his views on genetics. Today, this debacle of scientific thinking is now a short-hand for when politicians try to legislate mathematical and scientific truths. And lest one thinks otherwise, uneducated politicians with poor critical thinking skills are not endemic to the planet as the Indiana Pi Bill confirms.
Lysenko was a poor scientist, and was a political tyrant. His claims became embraced by the aparatachik, and this didn't only lead to the adoption of an alternative fact, but the incarceration and execution of his opponents in the debate. From WP:
More than 3,000 mainstream biologists were dismissed or imprisoned, and numerous scientists were executed in the Soviet campaign to suppress scientific opponents. The president of the Soviet Agriculture Academy, Nikolai Vavilov, who had been Lysenko's mentor, but later denounced him, was sent to prison and died there, while Soviet genetics research was effectively destroyed. Research and teaching in the fields of neurophysiology, cell biology, and many other biological disciplines were harmed or banned.
What Lysenko claimed was truth. What the opposition said was crime punishable by force.
Putin and Propaganda
A quick contemporaneous example would be how Vladimir Putin, in his 2022 invasion of Ukraine, has used RT and stifled dissent of claims of truth, and created an alternative narrative for the citizens of Russia and provided a pretext for the invasion, claiming the democratically elected government of Ukraine are Nazis who have engaged in ethnic cleansing of ethnic Russians. (A false claim at odds with the facts.) Now, while today with information and communications technology (ICT) it has become more difficult to deliberately create false narratives, since any one person can use a smartphone to relay the actual state of affairs to the global community, Putin has demonstrated that by imprisoning protestors, passing laws to forbid alternative narratives (even "true" ones), and by using propaganda techniques, it is still possible to hold an entire population in the dark on current events that they can't see directly with their own eyes.
The Philosophy and Politics of Science
In the philosophy of science, no work is more infamous for focusing a spotlight on the politics of the creation and defense of scientific truth that The Structure of Scientific Revolution written by Thomas Kuhn. The crash course is that scientific paradigms are largely political positions that shape what is known as normal science, and that the changes in paradigms is often a function of the politics that surrounds scientific practice. This idea was of course not new as was broadly embodied by Planck's Principle:
A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die and a new generation grows up that is familiar with it... An important scientific innovation rarely makes its way by gradually winning over and converting its opponents: it rarely happens that Saul becomes Paul. What does happen is that its opponents gradually die out, and that the growing generation is familiarized with the ideas from the beginning: another instance of the fact that the future lies with the youth.
Max Planck, Scientific autobiography, 1950, p. 33, 97
By the time Kuhn published, a number of philosophers of science went after the positions held by the logical positivists to argue that science wasn't formulaic, no principles certainly and clearly demarcated its practice, and that science was not a logical, orderly affair, a but a very ego-centric, haphazard, and messy affair. The last position was espoused by Paul Feyerabend.
Philosophy, Post-Structuralism, and Truth
Why is it that philosophy and philosophers often find themselves at the center of such conflicts? Well, philosophers, be they theologians or philosophers of science, lay direct claim to critical thinking skills, logic, and truth. That is, such thinkers often lay claim to what is true and not true, claim to possess expertise in what constitutes the proper use of reason, and spend considerable time and energy engaging the examination of evidence and using it in argumenation. While some people are willing to turn on the television and simply overlook a media outlet's unethical behavior, others engage what authorities present as truth with skepticism. And what are those who study skepticism called? Philosophers.
Post-structuralists simply take this to another level by rejecting many commonly held assumptions that inhere to popular worldviews. Post-structuralists take a hard look at 'facts' through a philosophical lens and divide them into truths about the physical world, and those that are abstract and socially maintained. From WP:
Post-structuralism proposes that human culture can be understood by means of a structure that is modeled on language. As a result, there is concrete reality on the one hand, abstract ideas about reality on the other hand, and a "third order" that mediates between the two.6 A post-structuralist critique, then, might suggest that in order to build meaning out of such an interpretation, one must (falsely) assume that the definitions of these signs are both valid and fixed, and that the author employing structuralist theory is somehow above and apart from these structures they are describing so as to be able to wholly appreciate them.
A post-structuralist, then, might study world history and the countless cosmogonies, and draw the conclusion, that 'truths' about where the universe comes from are completely relative to the culture. Such a thinker may even look at the Big Bang theory and draw the conclusion it is not necessary any better than a tale of Khaos and Kronos. Today, many physicists today subscribe the Multiverse Theory despite the complete absence of any empirical evidence. What is 'truth' after all, isn't so easy to tease out of argument, particularly for the uneducated, inept thinker, and everyone has their own agenda.