In early 1475 Constantine XI passed away at the age of 70 due to complications with pneumonia, leaving the Roman Empire in the hands of his son Ioannes IX. Ioannes was already aiding in the administration of the Empire as early as 1457, but was now the sole ruler of Rhomania. It was later in the year when he received envoys from the Coptic Church, speaking of the plight of the faithful in Egypt, and desired Ioannes aid in liberating them from the rule of the Mamluks, Ioannes was already considering an intervention around this time however, having been in talks with the rump Kingdom of Jerusalem about coming to their aid. The agreement signed between the two sides formally agreed that Jerusalem would become a client kingdom to the Romans upon the successful liberation of the Levant, and now Ioannes was given further incentive to expand his influence further at the expense of the Mamluks.
The Mamluk Sultanate had already faced the wrath of the Romans once before this century, having lost land in Anatolia to Constantine XI, who settled a peace with them after taking Antioch, further their control over the Sultanate of Medina was severed, weakening their position further. It is likely for this reason that they first attempted to make up for their lost territory by taking land from Jerusalem in the 1440s, as well as start their programs against the Copts. The Sultanate, unaware of the deal brokered between the Romans and Jerusalemites, began a campaign to take the rest of the rump kingdom soon after, which triggered Ioannes response to come to the aid of his new vassal by June.
Ioannes struck the Mamluks with three armies, and used the Roman fleet to provide logistics for a coastal campaign. Along with the Jerusalemites, they retook several fortresses and retook Tartus before expanding south at a rapid pace. With a Mamluk army pinned in the north he along with the Strategos George Bryennios marched south to pursue a retreating Mamluk army at Beirut, which was crushed while the city was invested by Bryennios. Ioannes continued down south and would then take Haifa where he would rest for the month. By March of 1476 a new Mamluk army would arrive to relieve the city, and Ioannes moved to intercept them at Caesarea in the Levant.
The two sides would skirmish and battle for a few days before Ioannes found himself surrounded by two armies, it turned out that this was an intentional ploy by the Mamluk general Al-Nasir to draw him out to get surrounded by an army that went around a longer path to take him in the rear. Despite being surrounded the Romans fought on hard to make it to Haifa, but during the battle a stray arrow managed to strike Ioannes in the throat, killing him instantly. Rather than be disheartened and break, the Romans under Ioannes found themselves enraged and fought a bloody and savage battle back to Haifa, where they would find themselves in a complicated siege.
George Bryennios learned of this incident and came to the relief of the besieged army, crushing the Mamluks and slaying Al-Nasir, avenging the deceased Emperor. With such a stunning victory, Bryennios was proclaimed as Emperor by his troops; Bryennios was hesitant to truly usurp the throne, but came to the conclusion that he could rule as co-Emperor, all he need was to get to any of Ioannes surviving children to help legitimize himself. With Bryennios departing the lower Levant, the war with the Mamluks entered a cold phase as the Romans couldn't progress without bringing more armies while the Mamluks needed a new army themselves.
However, new developments back in Constantinople were happening. Michael Doukas had launched a palace coup with the support of many Dynatoi, and had forced Ioannes 9 year old daughter Helena to become betrothed to his 14 year old son Iason while he took up the role as co-Emperor. Michael Doukas was able to find a great deal of support from the Dynatoi due to how much they disliked Ioannes tax reforms, and believed that Michael would make for a more "agreeable" Emperor. Already a Roman civil war had begun, as armies loyal to either side began to battle against each other.
While all this was occurring, the east was barely being held; when Ioannes initially launched his campaign, his brother Demetrios the Younger began his own campaign to conquer Aq Qoyunlu, with support given to him from the Armenians. His campaign however drew the ire of Qara Qoyunlu, which brought forth its entire might to crush Demetrios and possibly begin an expansion west. Syria would soon see a vast host of armies clash as Demetrios struggled to keep the Turkish forces at bay, the war in the east soon expanding into Armenia, and into Georgia, which was attacked by the Qara Qoyunlu vassal of Shirvan.
Qara Qoyunlu was able to commit such forces due to their long standing treaties with the Persians. During the decline of the Timurids a new Persian dynasty rose to come to power, the Efshanid Persians have become a notable power in the region and an ally to Qara Qoyunlu, but this alliance may not hold as the Persian Shahs seek to expand their power, an a largely defenseless frontier is an enticing target. Out west, the Duchy of Viden, a Bulgarian client state established during Constantine's reign, began to invade into Wallachia, supported by an army loyal to Michael Doukas, however the Vlachs had support from Ioannes oldest son Isaac, who while oldest, was born out of the Purple Chamber.
While the Roman Empire finds itself caught with two claimants to the throne, a third begins making themselves known. Romanos Palaiologos was visiting his Aunt Anna in Portugal when his father Ioannes died in battle, when news of not only his fathers death, but of the growing civil war reached him, he had little time to mourn and worry, and began recruiting mercenaries eager for some work, finding a few in Portugal and Castile. As the year 1476 nears it's end his stays in Genoa to recruit even more mercenaries and plot his next move, aware that a loyalist army exists in the former Kingdom of Naples in the south and that his brother is still active. It is fortunate that he is in Genoa, for they will be an opportune ally in his campaign, the Venetians have supported Michael Doukas.
As the year ends, the next two will bring Rhomania even further into chaos, as the Ninth Crusade is about to begin, and the trustworthiness of the Persians will be tested. The Mamluks will rebound and in the Northern Steppes the Great Horde looks on to decide what actions it will take in the growing Crisis of the 1470s.