What is a defining event in YN's history?

[Alternate Gallifrey]

A defining period in Gallifreyan history was the so-called "Imperator Era". While there were many things that made the Imperator Era infamous the most important aspect of the period was that it presented the first major change to the Great Houses culture in over two million years.

Many Time Lords considered the Imperator Era to be an ill omen for dark times ahead.... and they were right.

[Attawapiskatt]

The abolition of the monarchy, September 1st, 1975.
After a referendum, King Raleigh XIV stepped down and no new king was crowned, ending 157 years of history. The King was a figurehead anyway, only being as a representative of the nation.

1974 REFERENDUM
SHOULD ATTAWAPISKATT MAINTAIN THE MONARCHY
YES: 45.9%
NO: 54.1% ✔

[Veraguas]

I don't know about international significance, but one of the defining moments of Veraguas's history was the coup d'état of September 11, 2022.

Unhappily (and this is pure coincidence), this shares the same anniversary as the Chilean coup of 1973, but the two could not have been more different. The Chilean coup violently deposed a democratic government and installed a brutal dictatorship; the Veraguan coup deposed a deeply unpopular and corrupt regime without shedding a single drop of blood, and the Revolutionary Government Junta which took power has promised to initiate genuine democratic reforms as soon as possible.

[Luziyca]

The two main defining events in Rwizikuru's recent history was 2 December, 1946, when Rwizikuru became independent from Estmere, and 1 June, 1968, when the Rwizikuran monarchy was established by Izibongo Ngonidzashe, grandfather of the current King of Rwizikuru, Munashe Ngonidzashe.

[Crimson Tree]

On October 7th 2185, the Akagi Project had finally been completed, all the while sirens blared on the surface of Okinawa above the project site, a giant artificial cavern. Employees of Red Keep Solutions hurried to evacuate the 1.457 million residents to the eerily lit cavern, filled with empty arcologies which could sustain the Okinawan populace for generations to come. The research director, Dr. Chisana Akagi, the project's namesake, stood on her makeshift podium and cleared her throat.

On that day, Okinawa perished. From its ashes, Crimson Tree was born.

[Sinofarsis]

There are two major turning points in Sinofarsi history: the Battle of Bereket and the Sinofarsi Civil War

The Battle of Bereket took place in the year 604 between the Sinofarsi, led by Äiçýübýözdà, and the Sassanids. That decisive victory secured Sinofarsi independence and marked the beginning of Sinofarsis’ first dynasty.

The Sinofarsi Civil War took place between the years 2008 and 2013, when monarchist forces seized the northern half of the country from the Islamic dictatorship in the south. It would be a victory for the monarchist forces upon the restoration of Hūräç IV as Khagan.

[Golyna]

There are two major defining moments in history

The first major moment was the Golynan War of Independence. After Britain took control of Golyna, the native peoples and American settlers revolted, trying to form an independent state. After three years of fighting, the British gave up and left the country, including to occupied Eastlake Province, now ruled by Golyna.

The second major event is the Golynan Civil War between 1946 and 1949. The country briefly split in three, before the western half united to take the Eastlake Province in 1949. The war has lead to major changes to Golynan politics forever.

[Canvalland]

The Minutemen War (1908-1911):
The Minutemen War is the largest internal conflict that Canvalland has ever seen. Over 30% of the territory was once battlefields and more than 320,000 soldiers were injured or killed. The Minutemen War effectively destroyed the aristocratic class' influence on Canvish politics and led to the constitution of 1914. The war also ended the long-lasting aristocratic system that influenced the country for over 900 years and allowed the country to become a modern democracy.

[The Infernum]

A few come to mind...

The Rebellion Against the First Fallen:
Lucifers angels had grown divided, some wished to continue the war against heaven, while others wished merely to indulge themselves in infernal hedonism. These tensions would have grown into a conflict when the capital issued a decree demanding all were to come to Pandemonium and bring their iliaster (soul-energy) stores to be handed over to the Thrones to be later doled out as judged necessary for the war effort.

As the two sides and their demons met over the field outside the capital and issued orders to the demons, the two conflicting compulsiohs balanced out, and allowing the demons the moment to act freely which they used to turn on their makers and overthrow them. The Great Houses have hypocritically ruled ever since.

The Bileflot Conclave:
When the overthrown first fallen returned leading invasions from the Broken Lands to which they had fled, the Lords of the Houses all gathered in the city of Bileflot (after killing all its residents just to be sure) to discuss how to address the threat. They couldn't come to an agreement on how to confront the invaders, enraging Sturrach who killed Astyanath and Oblurott. This started Sturrach's War, as Sturrach's armies rampaged across the Infernum for almost two centuries, seemingly unstoppable in their conquest.

The Battle of the Ash-Ghosts:
Off all the things to stymie the march of the Sturrach, it was mere Damned. Upon reaching the Third Circle, the Sturrach marched upon the Haimon lands, and came to clash with a force of Damned Soul legionarres. Against all odds, the Damned turned the tides and took victory, enduring the assault, scattering the Sturrach soldiers and killing the general. The battle showed that the Sturrach were not unbeatable, galvanizing resistance against them. To this day, the date of the battle is remembered and a military leader having a string of victories up to this point is seen as a bad omen.

[Wochaystein]

The Trouble across the Four Corners is a major civil war between the supporters of the major sibling-claimants to the title of Emperor: Adalbert, Adaldunk, Grimbert, and Grimdunk. It was never resolved and caused the shattering of the Holy Empire. All of its successor states claim that they are the "true" Empire.

[Bededonia]

independence

[Farromia]

the Farromian Unification War ( 1030-1034 ) when Farromia was unified into one Kingdom

the 1853 revolution, when the repubblicans destroyed the monarchy and established the republic

the civil war of 1936-1939

[Sagrea]

By far, the most significant time for Sagreans is the "Lost Age", which lasted from 1866 to 1931. the 1108 year old monarchy had suddenly collapsed, seemingly overnight, and now their nation is simply territory to the neighboring empire. This period is not only significant for the loss of the monarchy, but for the gripping fear in all Sagreans that they no longer had an identity. Their customs, practices, and general way of life seemed to be under attack as they felt the practices of their new overlords would take precedence.

If not for this fear, Sagreans would not have had the government they do today. This fear pushed the ultranationalist movement that secured sovereignty in 1931, and what made the populace so agreeable to an authoritarian government, so long as it would respect the Sagrean way of life. The new national doctrine, Supremism, took the general values and customs of Sagrean culture and took them to extremes, in an attempt to ensure they continued to last. And finally, the nation would not be so keen on constant advancement, extreme specialization, and the constant search for the most competent people, if they weren't so utterly terrified at the thought that everything they had fought for would be lost again.

[Novarana]

There are 2 events that have happened recently that have possibly shaped the future of the UKN.

#1 - On December 10th, 2002 a meteor containing rare materials crashed into the wilderness of the Akamaya Mountains, what was notable was that the nearest settlement, Oykrowa, didn't see or hear anything, except a small blue trail, another thing was that the materials inside it boosted the technology of Novarana, but the Novan Government didn't say anything about it, theorists in the nation have said that it could be alien technology. After the event Novarana used the materials to improve the military and also saved the materials for when we are able to copy them.

#2 - Sometime after the Purple Meteor, Head of State, Alexei Korpov would form the "Novan Civil Intelligence Group (NCIG)", after this formation more and more people who talked down of him started going missing, though these were normally just average citizens, it started to get truly noticed after a member of the King's Royal Protection Service (KRPS) went missing, and when news stations published stories about it, they were quickly blocked, and then on September 9th, 2013, Alexei Korpov, the NCIG, and many notable corrupt officials otherthrew the King in what is now called "The September Coup", or what the government calls it "The Day of Victory", after the coup the royal family started shrinking and shrinking, and on January 12th, Prince Markia would be executed by the KRPS and NCIG, and a week later Alexei Korpov would become the "Novan King", he then formed a personality cult and spread propaganda all over the nation, he is now the "Eternal King of Novarana" and has started developing a futuristic military and have successfully cloned the material from the Purple Meteor.