Gunpowder

"We had never seen anything like it. How could we nothing like it has ever existed. The barking and thundering of their cannons was far faster than we ever had ever seen before. They tore apart our fortifications like it was nothing."

— Volimar II, last king of Estern.

The Fall of Estern

During the last war between Estern and Caliva, the Divine Kingdom, the latter unveiled their latest design of cannons, which greatly improved on previous versions especially in terms of cannon size and destructive capabilities delivering stone balls weighing more than a man, which tore apart Estern castle walls with unnerving ease.
With their new technological superiority, Calivan armies took one fortress after the next, conquering more than half of Esterns kingdom in mere months, where previously they would have taken years to even gain a foothold on one part of the border between the two rivals. The Estern crown and nobility mounted a valiant defense, but when the south and the west of their kingdom were taken and the capital was under siege, all they had left to fall back on were the more sparsely populated and less fertile norther lands.
When the capital fell in the early fall, with no hope of outlasting the siege into the winter, King Volimar II agreed to capitulation and in an unprecedented move agreed to swear fealty to his previous rival, no longer a sovereign nation, but yet another noble house of Caliva.
This war ended three decades ago.

Consequences

Within Caliva

With the conquest of Estern, Caliva as a Kingdom ballooned in size, adding new revenue streams but more importantly, plenty of land and citizens into their ranks. While much of the southern half of the kingdom was left in ruin after the war, the north including the suprisingly populous city Moondoor has flourished no doubt in part due to the influx of new wares, ideas and technologies including an improved printing press.
With its new size, Caliva has cement itself as a powerhouse of global politics, now able to field much larger armies and wield resources previously unattainable, something that has not gone unnoticed.

Internationally

Caliva's conquest of Estern was a warning shot for the remaining kingdoms, which they paid close attention to. If they hadn't been developing their own guns already, all civilized nations are now in a proper arms race to keep up with the rapid improvements in the fied. Almost on a yearly basis artillery records are being broken with larger guns now weighing multiple tons and firing devastating payloads.
At the same time, Caliva has reached a peculiar position in politics. It is so large that none of the other players dare to oppose it directly, but at the same time it is also considered so dangerous that no one dares leave them alone for too long. Calivan superiority in the development of gunpowder weapons has already brought one ancient house of old to its knees and people fear that if they stop paying attention, they may be next.

The future of warfare

What few people realise is that they are not looking close enough. While Caliva is actively participating in the arms race of making bigger and bigger weapons and it sometimes even seems that they are no longer as far ahead in the field as other nations, in secret something else is brewing.
Caliva has spent the last decades developing the next big leap of technology and are about to achieve it. A smaller, but much longer cannon is about to see completion. This new design is less volatile, but much more mobile than the commonly built behemoths, in combination with the longer barrel, they can propel their cannon balls much further at higher accuracy to boot.
This new Calivan design is not fully perfected yet, but once unveiled to the world stage may yet again upset the balance of power in a similar way their successes against Estern did.

"This is it. With this they can win the war. Before we can even hope to learn how to make them ourselves, they'll have conquered our lands. What folly that we didnt do the same. "

— Volimar II, three weeks before Esterns unconditional surrender.