Sorcerer Kingdom's Covert Invasion

Sorcerer Kingdom's Covert Invasion was the invasion of the Re-Estize Kingdom by the Sorcerer Kingdom during the conflict between the two nations. As the name implies, it was done covertly, with the Kingdom having no idea that war had broken out.

Background
Upon Albedo successfully "declaring" their date of invasion during their formal deceleration of war against the Re-Estize Kingdom in approximately one month from their deceleration, the Sorcerer Kingdom had in fact already sent out their armies to invade and conquer the Kingdom's northern and eastern territories and lands while completely leaving the western Area that contained the Royal Capital unharmed in order to further throw off their enemies from their actual activities.

This move was done under the suggestion of the Floor Guardian, Cocytus who had suggested it in order to isolate the Royal Capital from its remaining Allies. Cocytus' idea was met with approval by the Sorcerer King and his two intellectual confidants, Albedo and Demiurge who wholeheartedly assisted him in the sidelines by forcing the some of the nobles to join the Sorcerer Kingdom and completely manipulate the flow of information in order to conceal their invasion from the Royal Capital.

Such a decision was likely also done due to the Sorcerer Kingdom's tactical insight on the fact that the Re-Estize Kingdom had already begun making secret plans with their neighboring nation of the Argland Council State to create an alliance to defeat them. Through their consistent conquering of the Kingdom's lands that contained the Council State's Borders with the Sorcerer Kingdom, Nazarick was able to successfully put a stop to any form of alliance between the two nations, whose border with the Re-Estize Kingdom primarily lied in its northern front. Later it was indeed confirmed that the Argland Council State and the Re-Estize Kingdom themselves were still in the middle of their secret talks to create an Anti-Sorcerer Kingdom Alliance, talks that were thus then completely halted by the Sorcerer Kingdom's successful conquest of their borders with the Council State. Not only that but even the War's reason itself that basically made the Kingdom the ones responsible for sparking it effectively dissuaded the Council State from further solidifying their alliance. The conquest of the kingdom's borders also successfully put pressure on the Council State from interfering with their justified war of retribution against the Re-Estize Kingdom.

Battles
The exact events of these battles are unknown. However, it mostly ended with the same result: the Sorcerer Kingdom's forces massacred all inhabitants of the territory they invaded.

The battles were so one-sidedly in their favor that the Sorcerer Kingdom even used it as an opportunity to experiment with new battle tactics. For example: in one battle, an army of Elder Liches was used to bombard a city in submission. Another was to airdrop undead using their recently acquired Frost Dragons. Mare, meanwhile, would simply use his nature magic to flatten entire cities and killing their population in one go.

Demiurge was in charge of information suppression to prevent the Kingdom's government from becoming aware of the situation. By using his Shadow Demons, the Floor Guardian was able to create a vast network that sought to it that no soul who entered conquered territories left alive.

Not all conquests ended in massacres, though, as Albedo used the Sorcerer Kingdom's sheer infamy to threaten several nobles into defecting. One of these was Marquis Raeven, who selected other non-corrupt nobles to spare. These nobles would also aid with the information suppression by harboring refugees from fallen territories and preventing anyone from leaving their domain.

Aftermath
Overall, the success of the Covert Invasion was an overwhelming victory for the Sorcerer Kingdom from which the Re-Estize Kingdom never recovered. It effectively set up the events of the remainder of the war by separating the Kingdom from its allies and isolating the Royal Capital.

However, Nazarick's human sympathizers were outraged by their comrades' actions and pleaded with Sorcerer King Ainz to halt the slaughter of innocent civilians. This, along with wishing to see how the Floor Guardians would react to failure, prompted the monarch to lose a battle on purpose. Despite this loss, though, it didn't change the overwhelming success of the Covert Invasion.

On the Kingdom's side; while unaware of the invasion, the Sorcerer Kingdom's seeming lack of movement caused suspicion. After finally learning of the situation, the Kingdom's government fell into chaos. Despite this, though, King Ramposa III still hoped to settle the crisis diplomatically. However, to Prince Zanac the Covert Invasion had made the Sorcerer Kingdom's intentions clear, prompting him to overthrow his father and begin war preparations.

The Sorcerer Kingdom's blockade made it impossible to flee the Kingdom through conventional means. However, there were three instances where it was breached; both Tsaindorcus Vaision and Blue Roses got through using teleportation magic, as did the Slane Theocracy's Black Scripture through unknown means.