The last military campaign that Emperor Marko 'the cruel' personally participated in was in the storming of Aragon. The Knights of Calatrava were dealt a crushing blow with thousands of troops from the Serbian, Francian and Hispanian Empires laying siege to their Fortresses and decimating their pitiful order. Stubbornly they hold onto Catholicism to the bitter end, a truce has been signed - but they will no longer hold any power in the world. Props should be given where they're due however, they've resisted conquering by Muslims, Karlings and then Miroslavs for about two and a half centuries now. Pretty impressive cockroaches.
And I suspect this may be a bug, but something amusing happened. The Jomsvikings that were being kept in the Serbian Empire's Swedish territories managed to successfully raid the Serbian Empire's merchant outpost in Ostlandet. Surprisingly, they raided the family mansion of one of the merchant families, something that for all intents and purposes should be impossible.
The last military campaign that Emperor Marko ordered was the pacification of the Eastern Serbian Empire. Emperor Matijir of the Eastern Serbian Empire was a young child then, and sorely in need of help from a treacherous revolt whose conspiracy went as far as the Kings of Alania and as close as the barons beneath Matijir's feet. No other help from the other Miroslavs arrived. The Africans were busy fighting the Egyptians over Pelusa. The Francians busy fighting the Italians whilst the British were destroying Norway with Danish support. The Swedish were overthrown by Queen Karin. A lazy coward, Queen Karin was nonetheless a brilliant strategist and prone to furious rage - with native support she gathered the armies needed to overthrow the Serbian King and establish a non-Miroslav Sweden. Normally allies would be on hand to stop such foreign takeovers, but the Holy Serbian Empire was fighting to overthrow the Serbian Commonwealth's Emperor and Serbian Rus was invading the Serbian Commonwealth to hilarious ends.
This left only the Serbian Empire able to respond to the uprising in the Eastern Serbian Empire, with the revolt threatening to permanently split the Eastern Serbian Empire apart. 210,000 men were sent to pacify the region. This force included the Gusars and the Varangian Guard, and also had to stop the Persian Empire from attempting to seize Azerbaijan in the chaos.
Emperor Mihailo of the Commonwealth attempted to invade Serbian Rus to enforce the Commonwealth's de jure borders. 10 years later during an invasion by the Holy Serbian Empire, Emperor Drago of Serbian Rus invaded the Commonwealth and won. Just as the Emperors of Hispania held their capital in Calatrava to spite the Knights of Calatrava, the Emperor of Russia held his capital in the Commonwealth.
Emperor Marko might have been able to sort this issue out had he not started becoming senile, his mental faculties degenerating to such a point where a regency was required. The 6 year campaign in the Eastern Serbian Empire also left the Serbian Empire without the means to directly intervene in the Holy Serbian Empire-Serbian Commonwealth war, which was only worsened by Serbian Italia entering the war on the Commonwealth's side.
After Emperor Marko died, he passed the Empire down to Emperor Boleslav II. Unfortunately this is also during the time that Emperor Boleslav II was suffering stress and depression, leaving him less than capable to end the wars between the North African Miroslavs or the wars of the 9 Empires. One of his accomplishments was in regaining Serbian Sweden; it was conquered with the help of the Danish, Russian and Polish-Lithuanian Miroslavs, bringing peace to the squabbling rulers for a short while while Sweden was subjugated. This success invigorated Emperor Boleslav II, however his stress did not decrease - Marrakech had secured independence from the Empire of Hispania under the talented Prince-Archbishop Javen. Commanding the religious masses with furor, he won independence only to be in turn usurped by a nationalist Mauritanian revolution. Mauritania is now ruled by Sultan Aderbal the Liberator. It is yet to be returned to Hispania. This was not the only cause of stress for Emperor Boleslav II, as something far worse than independence happened.
Unification. During the regency of Emperor Marko and the wars of the Serbian Commonwealth, Emperor Mihailo of the Serbian Commonwealth married Empress Elenor of Italia. When Prince Simeon rises to the throne he will hold both Empires, and it is too late to stop this from happening. The Holy Serbian Empire tried to dethrone Emperor Mihailo while it was still possible, but were ultimately defeated by the joint Italian and Commonwealth forces.
The chaos of the East was compounded somewhat. The Serbian Empire and the Persian Empire provided great tracts of stability to the Christian and Muslim worlds, with the Persian Empire even finally managing to defeat the Orthodox Karesili Turkic tribes of the North.
Then the Ilkhanate attacked.
Ironically, if it wasn't for the Persians having seized the lands of the Orthodox tribes, they would now all be Khan food.
Attempts at civilizing the Mongols have been met with torture.
On the Miroslav front, Sultan Amud of Egypt is permanently aggravated by Emperor Boleslav II, as the Duchy of Antioch is now de jure Egyptian territory for some reason and Alexander remains in Serbian Empire hands. This is only made worse by Emperor Boleslav II's support of Sultan Issam of Africa, who holds de jure Egyptian lands in the Duchy of Pelusa and has so far been able to hold onto them in perpetuam due to Serbian Empire intervention. This is somewhat of an issue in that [particularly after Sultan Amud was kicked out of Jerusalem] Egyptian-Serbian Empire relations are at an all time low, and despite being much smaller than the Eastern Serbian Empire, have had a much larger role in curbing Muslim and Catholic aggression than any other Empire or Kingdom besides the Serbian Empire itself. Now it seems the Egyptians will only ever side against the Serbian Empire. After 300 years of Serbian Empire rule, it may be that Alexandra and Antioch may have to be turned over to the Egyptian Sultan.
The other option is that the Kingdom of Egypt be conquered, but that is somewhat difficult with the arrival of the Khan, and would likely be stopped by the advances of the Muslims or Catholics in the area.
Red cross = Miroslav
Mauritania will likely have to be conquered directly by the Serbian Empire. Serbian Norway no longer exists, having since been split between a Miroslav Trondheim and a non-Miroslav duchy. Persia still remains a powerful force and the Ilkhanate is only limited in expansion by a 10 year truce between neighbours. It is hoped that they will limit their conquering to the Persians and will continue to exist as a powerful barrier to the Golden Horde. Serbian Rus is beginning to become more powerful than the Serbian Commonwealth, this will likely continue to fuel Serbian Rus expansionism up until the Serbian Commonwealth and Serbian Italia unite.
Emperor Boleslav II has kept the Empire's coffers full whilst the Middle East Pope gambit has payed off, with the Papacy now being down 3k since it first began its reign. The Serbian Bank has recovered under King Zvonimir, whose predecessor has been exiled to Menckleburg. He is currently extremely stressed about being in this precarious position, but is expected to get a wife and sire a child before dying of stress, or else his female heirs will be murdered until a male heir is found and he is in turn executed.