In 1428 this event popped up.
I decided it was ripe to declare war on Denmark after reading over some comments on here. I moved my army to Småland, increased minting and prepared for war by raising an army 10,000 strong. On August 5th, 1429, Sweden declared war on Denmark, and King Erik XIII Sparre took the throne of Sweden.
On August 6th, Norwar, Burgundy, Trier, Aquileia and Luneburg declared war as well.
Novgorod offered an alliance shortly after Sweden declared herself independent.
In February 1430, the Norwegian Army attempted to attack Sweden. The attack was repelled and the Norwegian army annihilated. The earth was scorched in Smaland and Vastergotland as well as Varmland.
A new heir to the throne was born as the Norwegian armies were destroyed.
Oddly enough, scorching the earth didn't hinder the Danish war machine any! They captured Vastergotland and were working on Smaland!
An attack was ordered, and the two armies, equally matched in terms of leaders but with Sweden slightly behind in tech, fought on for months. In the middle of the battle, researchers found late land research was useless!
I was so close to getting the next level, I couldn't possibly afford a loss now! I opted to take the hit in stability rather than be left in the dust.
The Battle of Smaland ended in January 1431, ending in a very disappointing Swedish loss.
One crisis after another. The national bank was failing. The options were between paying 200 ducats (which I didn't have) or have inflation kicked up by 5. I couldn't possibly take the hit in ducats, so I grinned and beared the extreme inflation.
The Danish army chased me to Ostergotland, where I was once again defeated. Oddly enough, rather than chase me down, they resigned themselves back to Vastergotland. I still don't know the reason behind this. I needed to destroy someone to cheer me up, and the tiny Norwegian army next to me looked like the perfect target.
Then, in May 1431, Burgundy offered white peace. I instantly accepted.
In August, 1431, the war didn't move very much. I was recovering losses while Denmark and Norway kept assaulting forts. The Teutonic Order proposed an alliance in the same month, which I accepted as well. Neither wanted to help me for some odd reason...
When September 1431 rolled around, Swedish Peasants revolted in Stockholm! Danish forces abandoned their assault long enough to fight them, and I threw my forces in when they had defeated the rebels to add pressure.
This proved to be a bold move, but a very costly one. My army did not beat the already weakened Danish forces. If I retreated, they surely would have followed. The entire army was then destroyed while trying to rout. 13,000 men, my entire forcelimit, gone. I had no manpower to rebuild the losses. Waiting would have meant Danish and Norwegian forces would have overrun Sweden and ended in annexation. To make matters worse, another rebel army popped up in Lappland.
The war was over. I could not have possibly fought the Danes with a meager force of 1k soldiers. As much as I hated it, in February 1432 I conceded to Danish demands and accepted Denmark's personal union once more.
But, make no mistake. Sweden will rise against the Danish oppressors once more, and this time we will win. We will have the better army, the better tactics, the better will to win. Sweden will fight once more.