The Great War

The Rise of the Thalmor

Although is is not well known, Summerset Isle suffered from the Oblivion Crisis just as much as Cyrodiil and the other provinces did. The Altmer waged war against the Oblivion invaders, occasionally even crossing over to close down Oblivion gates.
The Thalmor were always a powerful faction within Summerset Isle, but had also always been a minority. During the Oblivion Crisis, the Crystal Tower was forced to give the Thalmor greater power and authority. Their efforts almost certainly saved Summerset Isle from being overrun. They capitalized on their success to seize total control in 4E 22. They renamed the nation Alinor. Most people outside of the Aldmeri Dominion still call it Summerset Isle.
In 4E 29, the government of Valenwood was overthrown by Thalmor collaborators and a union with Alinor proclaimed. Thalmor agents had formed close ties to certain Bosmeri factions even before the Oblivion Crisis. The Empire and its Bosmer allies, caught completely off guard, were quickly defeated by the much-better prepared Altmer forces that invaded Valenwood on the heels of the coup. Valenwood would serve as the Second Aldmeri Dominion's foothold on Tamriel. And thus was the Aldmeri Dominion reborn.

Shortly afterward the Aldmeri Dominion severed all contact with the Empire. For seventy years they were silent. Most scholars believe there was some sort of internal strife in Alinor, but very little is known of the factional struggles that went on inside the Dominion while the Thalmor consolidated its power in Summerset and Valenwood. It is also believed that during this time the Dominion and Valenwood were rapidly building up their armies for the invasion of the rest of Tamriel.
In 4E 98, the two moons, Masser and Secunda, vanished. Within most of the Empire, this was viewed with fear. It was far worse in Elsweyr. Culturally, the moons are much more influential to the Khajiit. After two years of the 'Void Nights', the moons returned. The Thalmor announced that they had restored the moons using previously unknown Dawn Magicks, but it is unclear if they truly restored the moons of just took advantage of foreknowledge that they would return.
Regardless of the truth of the matter, the Khajiit credited the Thalmor as their saviors. Within 15 years, Imperial influence in Elsweyr had so diminished that the Empire was unable to respond effectively to the coup of 4E 115 which dissolved the Elsweyr Confederacy and recreated the ancient kingdoms of Anequina and Pelletine as client states of the Aldmeri Dominion. Once more the Empire failed to stop the advance of Thalmor power.
When Titus Mede II ascended the throne in 4E 168, he inherited a weakened empire. The glory days of the Septims were a distant memory. Valenwood and Elsweyr were gone. Black Marsh had been lost to Imperial rule since the aftermath of the Oblivion Crisis and Morrowind had never recovered fully from the eruption of Vvardenfell. Hammerfell was plagued by infighting between Crowns and Forebears. Only High Rock, Cyrodiil and Skyrim remained properous and peaceful. Emperor Titus Mede had only a few short years to consolidate his rule before his leadership was put to the ultimate test.

The War Begins

On the 30th of Frostfall, 4E 171, the Aldmeri Dominion sent an ambassador to the Imperial City with a gift in a covered cart and an ultimatum for the new Emperor. The long list of demands included staggering tributes, disbandment of the Blades, outlawing the worship of Talos, and ceding large sections of Hammerfell to the Dominion. Despite the warnings of his generals of the Empire's military weakness, Emperor Titus Mede II rejected the ultimatum. The Thalmor ambassador upended the cart, spilling over a hundred heads on the floor: every Blades agent in Summerset and Valenwood. And so began the Great War which would consume the Empire and the Aldmeri Dominion for the next five years.
Within days, Aldmeri armies invaded Hammerfell and Cyrodiil simultaneously. A strong force commanded by the Thalmor general Lord Naarifin attacked Cyrodiil from the south, marching out of hidden camps in northern Elsweyr and flanking the Imperial defenses along the Valenwood border. Leyawiin soon fell to the invaders, while Bravil was cut off and besieged.

At the same time, an Aldmeri army under Lady Arannelya crossed into western Cyrodiil from Valenwood, bypassing Anvil and Kvatch and crossing into Hammerfell. Smaller Aldmeri forces offered only scattered resistance to the invaders, and much of the southern coastline was quickly overrun. The greatly outnumbered Imperial legions retreated across the Alik'r Desert in the March of Thirst.

4E 172-173: The Aldmeri Advance Into Cyrodiil

It appears now that the initial Aldmeri objective was in fact the conquest of Hammerfell, and that the invasion of Cyrodiil was intended only to pin down the imperial legions while Hammerfell was overrun. However, the surprising initial success of Lord Naarifin's attack led the Thalmor to believe that the Empire was weaker than they had thought. The capture of the Imperial City itself and the complete overthrow of the Empire thus became their primary objective of the next two years. As we know, the Thalmor nearly achieved their objective. It was only because of our Emperor's determined leadership during the Empire's darkest hour that this disaster was averted
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During 4E 172, the Aldmeri advanced deeper into Cyrodiil. Bravil and Anvil both fell to the invaders. By the end of the year, Lord Naarifin had advanced to the very walls of the Imperial City. There were fierce naval clashes in Lake Rumare and along the Niben as the Imperial forces attempted to hold the eastern bank.
In Hammerfell, the Thalmor were content to consolidate their gains as they took control of the whole southern coastline, which was in fact their stated objective in the ultimatum delivered to the Emperor. Of the southern cities, only Hegathe still held out. The survivors of the March of Thirst regrouped in northern Hammerfell, joined by reinforcements from High Rock.

The year 4E 173 saw stiffening Imperial resistance in Cyrodiil, but the seemingly inexorable Aldmeri advance continued. Fresh legions from Skyrim bolstered the Emperor's main army in the Imperial City, but the Aldmeri forced the crossing of the Niben and began advancing in force up the eastern bank. By the end of the year, the Imperial City was surrounded on three sides - only the northern supply route to Bruma remained open.
In Hammerfell, Imperial fortunes took a turn for the better. In early 4E 173, a Forebear army from Sentinel broke the siege of Hegathe (a Crown city), leading to the reconciliation of the two factions. Despite this, Lady Arannelya's main army succeeded in crossing the Alik'r Desert. The Imperial Legions under General Decianus met them outside Skaven in a bloody and indecisive clash. Decianus withdrew and left Arannelya in possession of Skaven, but the Aldmeri were too weakened to continue their advance.

The Sack of the Imperial City

In 4E 174, the Thalmor leadership committed all available forces to the campaign in Cyrodiil, gambling on a decisive victory to end the war once and for all. During the spring, Aldmeri reinforcements fathered in southern Cyrodiil, and on 12th of Second Seed, they launched a massive assault on the Imperial City itself. One army drove north to completely surround the city while Lord Naarifin's main force attacked the walls from the south, east, and west. The Emperor's decision to fight his way out of the city rather than make a last stand was a bold one. No general dared advice him to abandon the capital, but Titus II was proven right in the end.
While the Eigth Legion fought a desperate (and doomed) rearguard action on the walls of the city, Titus II broke out of the city to the north with his main army, smashing through the surrounding Aldmeri forces and linking up with reinforcements marching south from Skyrim under General Jonna. Meanwhile, however, the capital fell to the invaders and the infamous Sack of the Imperial City began. The Imperial Palace was burned, the White-Gold Tower itself looted, and all manner of atrocities carried out by the vengeful elves on the innocent populace.
In Hammerfell, General Decianus was preparing to drive the Aldmeri back from Skaven when he was ordered to march for Cyrodiil. Unwilling to abandon Hammerfell completely, he allowed a great number of "invalids" to be discharged from the Legions before they marched east. These veterans formed the core of the army that eventually drove Lady Arannelya's forces back across the Alik'r late in 174, taking heavy losses on their retreat from harassing attacks by the Alik'r warriors.

The Battle of the Red Ring

During the winter of 4E 174-175, the Thalmor seem to have believed that the war in Cyrodiil was all but over. They made several attempts to negotiate with Titus II. The Emperor encouraged them in their belief that he was preparing to surrender; meanwhile, he gathered his forces to retake the Imperial City. In what is now known as the Battle of the Red Ring, a battle that will serve as a model for Imperial strategists for generations to come, Titus II divided his forces into three. One army, with the legions from Hammerfell under General Decianus, was hidden in the Colovian Highlands near Chorrol. The Aldmeri were unaware that be was no longer in Hammerfell, possibly because the Imperial veterans Decianus had left behind led Lady Arannelya to believe that she still faced an Imperial army. The second army, largely of Nord legions under General Jonna, took up position near Cheydinhal. The main army was commanded by the Emperor himself, and would undertake the main assault of the Imperial City from the north.

On the 30th of Rain's Hand, the bloody Battle of the Red Ring began as General Decianus swept down on the city from the west, while General Jonna's legionnaires drove south along the Red Ring Road. In a two-day assault, Jonna's army crossed the Niben and advanced west, attempting to link up with Decianus' legions and thus surround the Imperial City. Lord Naarifin was taken by surprise by Decianus' assault, but Jonna's troops faced bitter resistance as the Aldmeri counterattacked from Bravil and Skingrad. The heroic Nord legionnaires held firm, however, beating off the piecemeal Aldmeria attacks. By the fifth day of the battle, the Aldmeri army in the Imperial City was surrounded.

Titus II led the assault from the north, personally capturing Lord Naarifin. It is rumored the Emperor wielded the famed sword Goldbrand, although this has never been officially confirmed by the Imperial government. An attempt by the Aldmeri to break out of the city to the south was blocked by the unbreakable shieldwall of General Jonna's battered legions.

In the end, the main Aldmeri army in Cyrodiil was completely destroyed. The Emperor's decision to withdraw from the Imperial City in 4E 174 was bloodily vindicated. Lord Naarifin was kept alive for thirty-three days, handing from the White-Gold tower. It is not recorded where his body was buried, if it was buried at all. One source claims he was carried off by winged daedra on the thirty-fourth day.
The White-Gold Concordat and the End of the War

Although victorious, the Imperial armies were in no shape to continue the war. The entire remaining Imperial force was fathered in Cyrodiil, exhausted and decimated by the Battle of the Red Ring. Not a single legion had more than half its soldiers fit for duty. Two legions had been effectively annihilated, not counting the loss of the Eighth during the retreat from the Imperial City the previous year. Titus II knew that there would be no better time to negotiate peace, and late in 4E 175 the Empire and the Aldmeri Dominion signed the White-Gold Concordat, ending the Great War.

The terms were harsh, but Titus II believed that it was necessary to secure peace and give the Empire a chance to regain its strength. The two most controversial terms of the concordant were the banning of the worship of Talos and the cession of a large section of southern Hammerfell (most of what was already occupied by Aldmeri forces). Critics have pointed out that the Concordat is almost identical to the ultimatum the Emperor rejected five years earlier. However, there is a great difference between agreeing to such terms under the mere threat of war, and agreeing to them at the end of a long and destructive war. No part of the Empire would have accepted these terms in 4E 171, dictated by the Thalmor at swords-point. Titus II would have faced civil war. By 4E 175, most of the Empire welcomed peace at almost any price.

Epilogue: Hammerfell Fights On Alone

Hammerfell, however, refused to accept the White-Gold Concordat, being unwilling to concede defeat and the loss of so much of their territory. Titus II was forced to officially renounce Hammerfell as an Imperial province in order to preserve the hard-won peace treaty. The Redguards, understandably, looked on this as a betrayal. In this, the Thalmor certainly achieved one of their long-term goals be sowing lasting bitterness between Hammerfell and the Empire.
In the end, the heroic Redguards fought the Aldmeri Dominion to a standstill, although the war lasted for five more years and left southern Hammerfell devastated. The Redguards say that this proves that the White-Gold Concordat was unnecessary, and that if Titus II had kept his nerve, the Aldmeri could have been truly defeat by the combined forces of Hammerfell and the rest of the Empire. The truth of that assertion can, of course, never be known. But the Redguards should not forget the great sacrifice of Imperial blood - Breton, Nord, and Cyrodilic - at the Battle of the Red Ring that weakened the Dominion enough to allow the eventually Second Treath of Stros M'kai in 4E 180 and the withdrawal of Aldmeri forces from Hammerfell.
There can be no doubt that the current peace cannot last forever. The Thalmor take the long view, as is proved by the sequence of events leading up to the Great War. All those who value freedom over tyranny can only hope that before it is too late, Hammerfell and the Empire will be reconciled and stand united against the Thalmor threat. Otherwise, any hope to stem the tide of Thalmor rule over all of Tamriel is dimmed.

Why Talos Worship was banned and the Markarth Incident

If you don't already know, Talos is the Nordic Hero-God of mankind and founded the first empire in the second era. When Talos died and ascended into the heavens, he was made a member of the divines. To the xenophobic Altmer, the idea of worshipping a man as a good is digusting, thus their reason for banning Talos' worship. Sometime after the Great War, the Forsworn took control over Markarth. The Jarl offered a small band of militia, lead by Ulfric Stormcloak, free Talos worship in return for assisting them in retaking the hold and the city. The Dominion caught wind of this, and forced the Jarl to arrest Ulfric and his men, branding them heretics. Otherwise, another war would unfold. During Ulfric's time in prison, his father died, and upon returning to his homecity, he became Jarl. Betrayed twice now by the Empire, Ulfric used this to justify the civil war in Skyrim.

Most of this info can bo obtained from a book in-game. I brought it up because I thought it was interesting, especially those who haven't read the book yet, interested in learning more about the Great War. It also serves for roleplaying purposes. For example, when I make a Red Guard, I am probably going to make them side with the Stormcloaks, as he/she will be a veteran of the Great War, and harbor a deep hatred for the Empire.

Nice info.

Personally I decided to side with the Empire despite our misunderstanding in the beginning. The Thalmer are the enemy and Ulfric wants us to fight each other. I found the arguments the pro-empire people made pretty compelling. Ulfric does seem a bit xenophobic too.

That said I did hang back and kill the torturer in the beginning. Torture is not cool. I do plan on taking out the Thalmer when I can as well.

Really good thread , even with reading the lore I've learned something new there.

The Empire just needs time to put itself back together. And the Stormcloaks aren't helping anyone.

Another good read is The Rising Threat. Supplements the great war by showing how the Thalmor came to power and just how they operate.



Rising Threat, Vol. I




I was barely more than a child when the Great Anguish fell upon us. The very air was torn asunder, leaving gaping, infected wounds that spewed daedra from the bowels of Oblivion. Many flocked to the shores, seeking escape from Dagon's murderous host - but the seas betrayed our people, raising up to smash our ships and our ports, leaving us to fates so vile and wicked that death would seem a mercy.
The Crystal Tower stood as our last bastion of hope, in both the literal and figurative sense.
Refugees filled the Crystal Tower until it could hold no more. I could taste the fear hanging in the air; feel the pall of despair suffocating us. We could see the daedra moving through the trees in the distance, but they did not come. Days passed, and still the daedra would not approach within arrow-shot of the battlements. Hope began to grow. "They fear us," some would say, "even a daedra knows not to trifle with the wisdom and magicks of the Crystal-Like-Law!"
It was as if the foul denizens of Oblivion had been waiting for this very spirit to stoke our hearts before they acted.
As we slept, innumerable legions of daedra amassed around us... and they were not alone. Hundreds of Altmer prisoners were gathered with them. As dawn broke, we were awoken by their screams as the daedra began to flail them and flay them. We watched in abject horror as our kinfolk were defiled completely... carved up and eaten alive, impaled on their depraved war machines, and worried apart as meals for their profane beasts.
This bloodletting was only a prelude to whet their appetites.
Once the daedra finished with our kinfolk, they turned their eyes to the Crystal Tower. Our great and noble bastion proved as much of an impediment as a mighty oak to a landslide - standing tall for but a few moments, appearing almost able to ride the tide of destruction around it, but ultimately being swept away.
Our exalted wizards decimated the fiends, roasting them by the dozens. Archers were finding the narrowest of chinks in their daedric armor at over a hundred paces, felling their captains and commanders. The might and skillfulness of our heroic defenders was astonishing to behold, but it was not enough. The daedra clambered over the corpses of their cohort. They marched headlong into death and destruction that would make the mightiest armies in all of Tamriel quake with fear.
When they breached the walls, I fled along with the other cowards. I take no pride in that act. It has haunted my existence ever since, and I burn with shame to admit it, but it is truth. We fled in mindless panic - abandoning those stalwart Altmer who held the line against the onslaught, to preserve and defend our illustrious Crystal Tower.
We raced through cleverly concealed passageways and emerged well away from the chaos that had descended upon the tower. That is when it happened. It started like a gust rustling through the leaves of a dense forest, but the sound did not taper off. It rose into a roar as the very ground on which I stood began to shudder. I turned to look, and the world held its breath...
I stood transfixed as the heart of my homeland was torn as if from my own briast. The unthinkable, the incomprehensible... the tower of Crystal-Like-Law cast to the ground, with all the dignity of a beggar meeting an iron-clad fist. An eternity I watched, trying to reconcile what I knew with what I saw.
Sobs racked my chest, and weeping filled the air around me as the spell loosened its hold and I realized where I was. There were scores of other refugees mesmerized by the horror that had likewise ensorcelled me. "Go," I croaked out as my heart - the heart of my land - shattered. No one moved, not even me.
I mustered what will I could and bellowed all the fear and hatred and agony at what had just happened, turning the word into a mindless shriek: "GO!" I ran then, feeling more than seeing that the others had followed.


http://www.imperial-library.info/content/rising-threat-vol-ii




What happened after the tower of Crystal-like-law fell was a daze. It was as if my mind simply...stopped. Instinct took over, as my every thought sank into a black abyss of despair. Time lost all meaning, and to this day I know not how long I was in this state. Eventually a conscious thought managed to break my fugue: the daedric horde had vanished! Gone as suddenly as they had come.
Before my numbed mind could comprehend the tulmut that had consumed my beloved Summerse Isle, before I could formulate the question “how?” they were there, dripping honeyed poison in our ears: the Thalmor. They were the ones that saved us, they claimed, working deep and subtle magics. It was their efforts, their sacrifices that delivered the Altmer from extinction.
Oh, what fools we were. We wanted so desperately someone to thank for ending out tribulations, we lavished it upon the first to step up and claim the glory. With that simple act of gratitude, we allowed a vile rot to seep into our homeland, to putrefy our once noble and distinguished civilization.
It was months before I began to suspect the error we had made. Small twinges of unease would vex me, but each one alone was easy enough to disregard and push aside. The exile of the great seer-mage Rynandor the Bold was the final doubt that I could not ignore. You see, Rynandor was one of the very few who survived the collapse of the Crystal Tower – I saw some of his bravery and heroics with my own eyes. It was his leadership and sorcery that made the daedra pay such a high price for their destruction of the Crystal Tower.
The Thalmor had besmirched his name when he had the audacity to publicly doubt and question their role in the ending of the Oblivion Crisis on Summerset Isle. Rynandor made the mistake of ignoring the consensus gentium, trusting instead to logic and facts. The shrewdness of the Thalmor, however, was not such to allow something as trivial as the truth to stand in their way. As soon as they shifted the collective opinion ever so slightly against Rynandor, they had him sequestered and intensified their efforts to tarnish his reputation. Unable to mount any sort of defense to the Thalmor's attacks, Rynandor was quickly denounced and exiled.


http://www.imperial-library.info/content/rising-threat-vol-iii




Ever so cautiously, I formed a cabal made up of others who distrusted the motives and methods of the Thalmor. Over several months, I liquidated my ancestral holdings and took whatever inheritance I could without raising any suspicions. I would follow after Rynandor and help him restore his reputation and status. We would then return to best the Thalmor at their own game and win back the mores and morals of the Altmer! The rest of my cabal would stay on Summerset Isle and win the trust of the Thalmor on whatever level best suited each of them, sending clandestine missives to me when possible.
After weeks of painstaking investigations and exorbitant bribes, I was able to learn that Rynandor was place on a ship to Anvil. I booked my own passage to Anvil. My search almost ended there, for Rynandor had never arrived in Anvil Harbor. My instinct that Rynandor met a duplicitous end was confirmed when I sought out several deackhands who were reported to be aboard Rynandor's vessel. All died under mysterious and violent circumstances.
The first of many attempts on my life occurred soon after. Needless to say, I survived, but my grand pla to stymie the Thalmor fell apart without an esteemed leader to rally behidn. I went into hiding, waiting anxiously for word of the Thalmor's activities back in on Summerset Isle.
Over the following years, I tried to bend the ear of the Empire through various avenues and war them of the Thalmor's doings. The Empire, however, was having enough troubles dealing with the aftermath of the Oblivion crisis within its own borders without seeking trouble in far away Summerset. With the assassination of Emperor Uriel Septim VII and his heirs, and the self-sacrifice of Martin Septim (the true savior of Summerset Isle and the rest of Tamriel!) the Empire's leadership was left defunct.
High Chancellow Ocato convened the full Elder Council in an unsuccessful bid to select a new Emperor. Without an Emperor, the Empire beyond the reach of Cyrodiil began to splinter. Ocato reluctantly agreed to become Potentate under the terms of the Elder Council Charter until Imperial rule could be reestablished, but a reluctant leader is rarely a strong leader.
Potentate Ocato made admirable efforts ot rein in the bedlam that threaded to rip the Empire apart, and was even making headway when Red Mountain erupted and destroyed much of Vvardenfell (likely from Thalmor tempering, but I have yet to find proof of their misdeeds in this). What was left of Morrowind was thrown into absolute chaos. The effects of the eruption were felt even in Black Marsh, destroying roads and cutting off Imperial garrisons there.
None were prepared for what happened next.


http://www.imperial-library.info/content/rising-threat-vol-iv




While Morrowind and the Imperial forces in Black Marsh were still reeling from the consecutive catastrophes of the Oblivion Crisis and the destruction of Vvardenfell, the Thalmor incited the Argonians to mount a massive uprising. Black Marsh and southern Morrowind were completely lost to the Argonians, but luckily the Thalmor too lost what influence they had over the reptilians.
All the while, the Thalmor consolidated their hold over my beloved homeland.
It took almost a decade before my own machinations put me into contact with Ocato. He seemed more interested than most in what I had to say about the Thalmor, maybe because he was himself an Altmer and recognized the threat they represented. It wasn't long before the Thalmor had Ocato assassinated.
Potentate Ocato's murder began the Stormcrown Interregnum. The Elder Council fractured, leading into years of ruthless in-fighting, plots and backstabbing. Many tried to claim the Ruby Throne. Most were pretenders to the crown, a few had legitimate claims, others still were little more than brutal dullards who thought mere strength of arms was all the entitlement they needed. Violent, unnatural storms lashed the Imperial City several times during this anarchy, always with the eye of the storm looking directly down upon White-Gold Tower, as if this was the judgment of the Nine Divines.
With the Empire submerged in this mayhem, the Thalmor were quick to act. They overthrew the rightful Kings and Queens of the Altmer. I remember the revulsion and horror that took hold when word reached me - that this dementia had gripped my homeland. Once so proud and majestic, many of our great race actually embraced this insanity!
Then the first of many pogroms descended on Summerset Isle. They slaughtered any who were not "of the blood of the Aldmer". A fine excuse to purge the dissidents, as well - the Thalmor have never been ones to waste such an opportunity.
After seven long, bloody years the Stormcrown Interregnum was ended when a Colovian warlord by the name of Titus Mede seized the crown. Whether he had rightful claim or not is moot. Without Titus Mede, there would not be an Empire today. He proved a shrewd and capable leader, such that Skyrim endorsed him as Emperor.
With the Empire stabilizing under the auspicious efforts Emperor Titus Mede, I resumed my efforts to warn them of the Thalmor threat. Again, the Thalmor remained a step ahead. Before my efforts could come to fruition, the Thalmor struck: another coup, this time in Valenwood. The Empire was not prepared for the Thalmor's subterfuge and stratagem.
There are those who claim the combined Altmer and Bosmer forces greatly out-matched the Empire, but this is a farce. This short, savage campaign was won by the Thalmor even before first blood was drawn. They waited and watched their enemy, they chose where and when they would attack. The Thalmor were able to bring the full fury of their small contingent of Altmer and Bosmer to any of several Imperial strongholds.
Contrary to the posturing of the Empire's generals, the Thalmor did not command greater numbers. They had better spies and greater mobility, and knew how best to use them. This is the menace that the Thalmor represent! They are cruel and merciless, but they are no fools! They are devious and subtle, and so very patient.
In one fell stroke, the Thalmor took a strategic foothold on the mainland of Tamriel and prevented any significant attempt the Empire could have made to invade Summerset Isle and depose the tyranny of the Thalmor. At the same time, they took a better vantage to continue to watch the Empire and wait. In so doing, they also revived the Aldmeri Dominion with their alliance to the Bosmer of Valenwood!
Over the decades, the Thalmor have grown quiet - but this is not the end. It has only just begun. They merely consolidate their power and tighten their grip on the hearts and minds of the Altmer. The Empire may wish to forget the wounds its pride has suffered at the hands of the Thalmor, but they are still out there. Plotting. Watching. Waiting.
While the Empire is content to secure inconsequential corners of its vast holdings, the threat of the Thalmor continues to rise. Not since Potentate Ocato has anyone in the Empire listened to me. I beseech any and all citizens of this renowned Empire to heed my words! The Thalmor must be stopped, before it is too late.
***
Soon after Lathenil of Sunhold commissioned to have these volumes printed and distributed far and wide in the Empire with his own coin, he himself met a violent end. In light of the events that followed his death, we must consider that he may very well have been murdered by Thalmor assassins.
-- Praxis Erratuim, Imperial Historian

It's a bit deeper than that. Talos is an anchor for humanity in the mythic. In order to erase their pattern from the possibility of existence, Talos has to be eliminated. Because of how worship works in Tamriel, lessening worship of him weakens his power.

According to Jarl Igmund, it was during the Great War, when the empire pulled their forces out of the region and sent them to support the Imperial City.