Era one: 910 to 1180, Byzantium's reclaiming of glory
This Alternate History looks at what could have happened if the Turks did NOT regain Central Anatolia. This period, which spans 910 to 1680, is divided into four "eras" of Byzantine Imperialism.
In this AH, Byzantine inflicted cruising military defeats on the Turkish armies sent against it, and not only kept her borders but enlarged them, encompassing all the land up the eastern Black Sea to traditional Colchis (whose people she vassalised), and down to Jerusalem and then Egypt, both of which became vassals. Without the Crusades to unite them, the people of Northern and Central Europe fell on each other, and out of the ashes rose a new superpower, Gallica, created by a revolt from the populace of the Frankish kingdoms. The Normans were inducted into the kingdom, thus giving them no chance to attack southern Italy. With Gallica on the rise, the waning powers of the Holy Roman Empire were no match for it, and the king of the Holy Romans, Philippius, fled to the court of Constantinople to ask for protection. The emperor, Leo the Great, accepted and in return placed the Holy Roman kingdom under a puppet government. After allying with the Gauls, Byzantine turned its attention further east, to the Iberian peninsula. Leo launched a 6 year campaign to free it from Muslim rule, and returned victorious. Iberia was far enough away from the main focus of Byzantine affairs, the Arabian peninsula, that instead of annexing it, they helped the citizens create a new government, and left the country of Iberia to its own devices. The general-king of the new nation of Iberia was extremely competent, and quickly conquered large swathes of African territory, mostly in Morocco. Leo's armies then took over Tunisia, and directly placed it under the authority of the Emperor.Meanwhile, the Fatamids had managed to take over Seleucia, and hold on to their status as rulers of the area, destroying the Seljuks in the process by convincing Byzantium that they were a greater threat than they were, and enlisting their aid. With the Seljuks soon gone, the Fatamid empire annexed Armenia as a vassal to counter Byzantium's annexation of Colchis. Tensions soon ran high over borders in that area, and the Fatamids and Byzantium were at war again. In the north, Novgorod and Kiev had rose in the absence of southern invaders to become two huge kingdoms that divided the modern Soviet frontier in half. In Denmark, the Saxons still ruled and had slightly expanded south. They were able to expand south and east because, following the Holy Roman Empire's disappearance in major politics, and shrinking of her borders, Poland and the area around it collapsed. From it arose the Teutonic Poland-Lithuanian Kingdom, which was at war almost constantly due to surrounding powers questioning its right to even exist. South of that was Hungary, who had been sent a request from the Byzantines to ally so they wouldn't threaten the Byzantine borders while Leo was fighting in the Iberian peninsula. They gladly accepted and began expanding their own borders now that their southern flank was secure. In England, the Anglo-Saxon kingdom had, with Gallic support, reduced Ireland down to a bloated Duchy of Munster. The Gauls supported the Anglo-Saxons because their crown prince had just gained rights of the Isle of Man through marriage, but it had recently been retaken by the Irish, and they were refusing to turn it over to the Gauls. Around 1120, Europe's nations stopped their conquests simultaneously, and the Western World entered what some scholars call "the rest period". But it was not to last. When Leo II died in 1119, he was succeeded by his sun, Leo III, who was mostly concerned with keeping Byzantium together. When he died with no successor, there was a short, but bloody civil war between the North and South halves of the Empire. The north won, and in 1176, their candidate, a son of an influential nobleman, Epheserus, came to power.
era 2: 1180 to 1348, Byzantium's apex and first downfallMost historians mark this period's beginning with Byzantine's marriage into the house of Gaul. The official dowry was to be a large chunk of southern France, which Gaul was, understandably, reluctant to give up. The Byzantine Empire took swift and brutal action; the crown prince marched to Paris with an army of 6,000, and deposed the king. One of the prince's little brothers was put in place as ruler of Gaul. Though not technically part of the Byzantine Empire, Gaul would henceforth be ruled by a Byzantine royal line. Unfortunately, as the crown prince was passing through Hungary, he was murdered by men wearing the Royal Hungarian coat of arms. Byzantine instantly declared war on Hungary, and in a space of weeks had captured most of its south, through a series of decisive battles, the most crushing to the Hungarians was the Battle of Koposvar. In desperation, Hungary signed a peace treaty that ceded Byzantium all of its colonies on the Black Sea, all of its Black Sea Coast, and quite a bit more land in the south of the country. Meanwhile, the new royal house in Gaul's first great act was to annex the entire Iberian peninsula. They would've conquered all of the new nation, Iberian Morocco, except that Byzantium agreed to grant them protection in exchange for some of its eastern holdings. Byzantium seemed very focused on the south in this Era. It practically wiped the Fatamids off the Arabian Peninsula, officially annexed Egypt, and began an invasion of the Bedouin tribes people in central Arabia. It also began expanding its hold over Libya and Tunisia. Meanwhile, further north, Colchis and Armenia were completely seized by Byzantium in 1191, and in 1193 the Holy Roman Empire was added to the list of direct territories of the Empire, in the costly Italian War. While Epheserus campaigned in Africa and Arabia, one of his leading generals, a Greek by the name of Hektor, was fighting further north. He was the one who had conquered Armenia and finished Colchis, and in 1194 captured Kiev. It was given vassal status, and 2/3 of its people were deported for use as laborers in its now huge expanses of land. Past the borders of Byzantium, the Teutonic Poland-Lithuanian kingdom had collapsed in a civil war, with Poland arising as the victor. Unfortunately for them, kingdoms such as Gallica, Saxony and Novgorod capitalised on the civil unrest to expand their borders further in. In the Anglo-Saxon kingdom, Munster was defeated in 1189. In this war, Byzantium had supported the Anglo-Saxons, in return for their help, Anglia, as it was called by the people living it it, ceded the Balaeric islands to Byzantium which interestingly had belonged to them for a few years due to a complex claim through several generations of relatives which turned out to be correct, and besides, most of them were Iberian to begin with and they didn't have the strength to resist the Anglian's insistence. With this land gained, Byzantium was at its peak. It would remain with these borders for about 40 years, until 1241. Epheserus had died of natural causes, and been replaced by his son, Epherserus II. Unfortunately for the empire, he lost several wars against Novgorod and the Italian rebels, eventually ceding most of Kiev to Novgorod in 1253, and being forced to recognize the independence of Venice and Florence in 1256. In Arabia, the Fatamids were pushing North and had conquered almost up to the Bedouin-Byzantine border by 1257. In the north, the Saxons were getting further and further south through Poland, but most people payed no attention to that due to another war in the West. The Anglo-Saxons, for not discernible reason, seized the Isle of Man in 1259. Gaul demanded its return at once, but Anglica refused to comply. Gallica declared war on Anglica and began invading the south. Seizing their chance, both Scotland and a good portion of Ireland rebelled, forming a triple alliance with each other and the Gauls. Anglica, it seemed, would soon be no more. However, the Anglo-Saxon fleet docked in Wales had grown to one of the best in the world, a fact that the crafty Anglican king William II exploited. He sunk a fleet of re-inforcements coming from Gallica to Ireland, and then cut off all supplies to the Gallic army. To force the Gauls on the island into submission required an unfortunate strategy; torching every field in advance of the Gallic army, preventing them from getting any food. On April 27, 1260, the Gallic army surrendered and was sent back home. Without Gallic support, the Irish and Scottish rebellions were quickly crushed and the Anglo-Saxon borders returned to much as they had been before the war, except that they now possessed the Isle of Man.
More to come...