- Main article: Imperial Legion
The Fourth Legion of Black Marsh was a division within the Imperial Legion. Initially led by a "young and charismatic" commander named Augurius Bucco, it fought during the Imperial invasion of Black Marsh, known as the "Blackwater War."
During the Blackwater War, which started in 1E 2811, it became obvious to Imperial forces that the Fourth Legion's equipment was not intended for use in the swampy, moist climate of Black Marsh; much of their armor was heavy and prone to rust. By late 1E 2812, some Legionnaires had completely abandoned significant portions of their armor due to the lack of comfort stemming from the weight and subsequent intense heat caused by the armor.
Like their extremely inadequate armor techniques, the Fourth Legion's battle tactics proved disastrous in Black Marsh. Due to the region's typically swampy and inhospitable geography, the Legion had serious trouble with organization, especially during battle. The uneven and thick terrain meant that their use of "rigid line organization" in clearer areas was no longer applicable. The lack of unity meant giving orders on the battlefield was difficult. This in turn led to numerous failures in battle and many desertions. Thousands of Legionnaires ofthe Fourth Legion would die during the war because of the Legion's unpreparedness.
By the year 1E 2816, all that was left of the Fourth Legion were six ragged cohorts. Morale steadily declined as losses in battle, disease, and disappearances afflicted the Legionnaires. By 1E 2820, the Fourth Legion had been almost entirely destroyed, and the few remaining soldiers could not last much longer.
At one point, the leader of the Fourth Legion, Augurius Bucco, was almost deposed as commander, and orders to withdraw from the deep swamps of Black Marsh were issued. The remnants of the Legion—just over 350 soldiers—made a stop at an ancient Argonian pyramid known as "Xi-tsei" on the tenth day of withdrawal, with the intention of continuing the retreat onward to Cyrodiil. However, on the night of Last Seed 14, 1E 2820, the few surviving troops were all killed, presumably by Argonian forces. Mysteriously, the bodies of roughly 150 of them were never discovered, and no indication whatsoever of their whereabouts was recorded.
After word of the Fourth Legion's utter annihilation reached Cyrodiil, the Fourth Legion was reconstituted by the Imperial Council, this time commanded by General Regulus Sardecus. Thus began the second campaign of the Blackwater War.
Under Sardecus' leadership, the newly-recreated Fourth Legion quickly resumed fighting in Black Marsh, regaining all previously-lost territory by 1E 2823. This is largely credited to Sardecus' orders that Legionnaires were to switch out their metal armor for "padded leather jackets," which were more suited to the Argonian climate. Additionally, efforts were made to improve communications between Imperial quartermasters, scouts, and Argonian "irregulars". The Legion learned how to live off the land rather than rely purely on imported supplies.
Sardecus also decreed that Centurions and Legates were to be allowed more control over their own groups of soldiers, thus allowing for more organized independent fighting. Sardecus was also quick to strip a soldier of their rank if they did not adhere to his methods. This system served to both improve the efficiency and the morale of the Legionnaires.
The most successful way that Sardecus overcame his opponents was actually through diplomacy rather than brute force. Unlike his predecessor, he was aware that the Argonians were not in fact a fully unified, barbaric people. Many influential tribes who were considered "disenfranchised" (such as the Archeins and Shoss-kaleel tribes) were offered various rewards for assisting the Legion in its conquests. In some circumstances, even full military alliances were formed. nearly tripling the Legion's manpower, and at last giving the Imperials a great advantage in the war.
The militaristic strategy of Sardecus and the Fourth Legion worked on the idea that the Argonian swamps were the most dangerous force to be faced. The strategy also focussed on rendering sources of food, cover, and travel useless to the Argonians.
After setting ablaze an expansive underground tunnel system, the Legion realized that the tunnels had been much father-reaching than anticipated; what started as just another attack led to much of the region being entirely engulfed in flames. As a result of the fire, hundreds of Legion soldiers and Argonians alike were devastated by frequent deaths by "swamp lung" and gas explosions, leading to a second retreat and subsequently Sardecus' death by an "infected wound" during the return to Cyrodiil.
The Fourth Legion's strategy had again been altered by 1E 2833, at which point General Lucinia Falco had succeeded Sardecus as commander of the Fourth Legion. Falco split up her soldiers into hundreds of small, highly lethal groups, later called "redbelts", in place of the full Legion. The prowess of these so-called "redbelts" was strengthened by the experience and knowledge of "grizzled swamp veterans," some of whom had been fighting in the war since the second campaign.
Although much progress was made at the beginning of the campaign through the use of this system, captured territory was held very loosely by the Fourth Legion. Eventually, the conflict escalated to an all-out guerrilla war, and tactics such as fierce intimidation were often used. By late 1E 2836, however, the Argonians abruptly ceased fighting, and by 1E 2837 the Empire had effectively secured full control over the region.
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