For Part One go here
For Part Two go here
For Part Three go here
For Part Four go here
Finally, what conclusions may we gather about Byzantine economy and society?
Byzantium originally started out as a continuation of the Late Roman Empire of Constantine I the Great (r. 306-337), so much her own citizens, despite shunning Latin and practicing forms of Christianity which diverged more and more from Western European Catholicism, called themselves Romaioi, Romans. The Late Roman Empire had nothing of the prosperous realm of Trajan described by Pliny the Younger. It was much poorer, much less secure and much less free. The State was everywhere, meddling in trade, pricing and religion. There was of course an exception to this rule, namely the Middle East: Syria, Palestine, Egypt etc. While Europe descended deeper and deeper into the interminable cycle of civil wars, the Middle East was an area of relative stability.
While the Galliae and Hiberia were ravaged from end to end by marauding armies and robbed of their accumulated wealth by ravenous tax collectors, Syria, Egypt and the other Middle Eastern lands remained relatively peaceful and stable.
The Arabs to the South were usually well disposed towards Rome (mostly thanks to generous “subsidies”) and on this frontier only one power faced the Empire: Sassanid Persia, heir to the ancient and highly advanced Iranic civilization.
The relationship between the Late Roman Empire and Sassanid Persia would deserve a treatment far beyond my skills. For two centuries the two great powers reached a detente (broken only by limited military campaigns and the occasional cattle lifting raid) because the highly disturbed conditions of the Eurasian Steppe sent waves after waves of plunderers and would be invaders crashing against the two Empires. The VI century saw a resurgence in Roman-Persian hostility, an hostility which climaxed in the interminable war which defined the first half of the VII century.
And just eight years after Heraklios had forced the Shah to accept peace, his armies suffered a catastrophic defeat at the hands of the Muslim Arabs at Yarmuk. 
This event had enormous repercussions at every level for Byzantium: less than a decade after winning her first struggle for survival, another serious menace had emerged. Syria and Egypt, the wealthiest provinces, were lost forever and in 671 the Arabs were already under the very walls of Constantinople. To make matters worse until the highly capable Leo III took power (arriving in Constantinople mere days before the Arabs in 717), Byzantium knew a series of despotic and ineffective military rulers and would be usurpers who not only proved ineffective at stemming the Arab tide but wrought great damages on the Empire with their senseless economic policies, tight controls and obstinate religious persecution. 
It can be said the siege of 717-718 was the lowest point in Byzantine history until the days of the “wretched” Angeloi. Leo III not only defeated the Arabs in such decisive fashion they never made another serious attempt at conquering the Empire again, but put order in the Imperial finances and set the basis for Byzantium’s rebirth in the IX century. The Late Roman pattern of heavy handed State interference started to recede.
This process accelerated under Leo VI the Wise (r. 886-912). An unjustly maligned ruler, he put the move towards a freer and wealthier society in high gear. Under his rule the edicts of Basil I which forbade interest charging and attempted to limit long distance trade were abolished. Venetian and Amalfitan traders, as nominal Byzantine subjects, were allowed free access to the Empire and Byzantine merchants started to expand their network in Muslim-dominated lands.
The Late Roman/Early Christian mentality, ideologically opposed to interest charging and private enterprise, died out in this period.  Incidentally the X century also saw a resurgence in commerce throughout the whole European Continent. While in Byzantium’s case it was improved safety and economic conditions, in Western Europe it was the collapse of the Carolingian Empire and the defeat of the Magyars at the Battle of Lechfeld in 955 by the Otto I of Saxony which brought this about. 
While the X and the XI century saw taxation increase to finance military campaigns (on the average highly successful), State-control over the economy and the society continued to recede. Taxation, while higher than before, was far from the crippling rates set by Justinian to finance his Imperial ambitions. Byzantine agriculture and industry kept growing at a frantic pace, thanks in part to Europe’s appetite for luxury goods and the mediation of the Venetians.
While Byzantium’s fortunes took a turn for the worse after the Battle of Manzikert (1071), the Empire had the human and financial resources to recover. The various usurpers and strongmen who succeeded Romanos IV Diogenes (r. 1067-1071), the vanquished of Manzikert, had only a limited effect on economy and society at large despite their “best” efforts.
This is mostly due to the appearance of Alexios I Komnenos (r. 1081-1118), the man who single handedly saved the Empire. It appears Alexios had at least an intuitive understanding of economics. He understood too much State meddling hurts all parts involved, including the State itself which sees revenues fall. He understood the potential of Byzantine economy and gave it a monetary and commercial system which allowed it to literally boom. Most of all he understood Byzantium was not located in a bubble, but was part of a rapidly changing world in which long distance trade (at least until the arrival of the Black Death and the collapse of the Pax Mongolica around 1350) was becoming more and more important. Even when Byzantium was at war with the Turks and the Arabs, Muslim traders were allowed to continue plying their trade in Constantinople herself and Byzantine traders were allowed to do the same in Cairo and Syria. This is part of that Old World mentality which was summed up by Louis XIV in the phrase “I am at war with the King of England, not mankind”.
Of course the Komnenoi were far from perfect: to obtain naval aid Alexios granted Venetian merchants “unheard of” privileges which ended up making them the supreme mercantile and naval power in the eastern Mediterranean. His son John (r. 1118-1143) initiated the odious practice of granting family members and personal allies positions from which they could “ransack” the society at large at will. While this practice was apparently limited, it did a lot to alienate the Komnenoi and destroy their well earned reputation as flawless “saviors of the Empire”. Manuel (r. 1143-1180) abandoned his grandfather’s policy of small military campaigns with limited objectives and intense diplomacy in favor of grandiose military expeditions which cost Byzantium her treasury and her armies.  Manuel also sowed the seeds of the Fourth Crusade: he hated the Venetians with a burning passion and attempted to hamper their commercial activities at every turn. By this point Venice was not just another trading republic, but the foremost naval power in the Mediterranean and an incredibly wealthy city. The Fourth Crusade was not just a spur of the moment decision by Venice to take advantage of Byzantium’s weakness, but a venture carefully planned years in advance. Venice had the ships and the money for the venture: all she needed were the troops. The Crusaders, swayed by promises of easy loot and the possibility of carving out a kingdom for themselves, were easily persuaded to provide them.
The Latin Empire (1204-1261) was a pathetic entity. Its Flemish rulers controlled little more than Constantinople herself, a city depopulated by a mass exodus towards those areas (chiefly Epyros and Nicaea) where Byzantine rulers stubbornly and bravely held out against both the Turks and the Latins.
This period of history has been called “Fragmentation”: the Empire broke down in three main nations, all claiming to be the legitimate heir to Constantine’s throne (the Empires of Nicaea and Trebizon and the aforementioned Latin Empire) and bewildering array of principalities, despotates, fiefdoms and colonies, ruled by both Byzantine nobles and various Western adventurers. Yet Byzantine economy kept on growing stronger and stronger. The much reduced weight of the State allowed economic activity to flourish and the presence of aggressive foreign merchants, eager to satisfy customers clamoring for exotic goods, allowed trade to literally explode.
At the start of the XIII century, however, something incredible happened. Temujin, the son of a small clan leader in Mongolia, had managed to unite both the warring Mongol clans and the sundry nomadic people of the area in a formidable confederation whose exploits completely rewrote history. Westerners know him by his Persian title: Genghis Khan.
Initially Temujin was of little concern to Byzantium, the Holy Roman Empire, Egypt, the Caliphate of Baghdad or other Western kingdoms: the Eurasian Steppe has produced an endless succession of adventurers and all these powers knew how to deal with them. Or at least they thought they knew.
By 1260 Temujin and his family had built an Empire which spanned from the Yellow Sea to Ukraine. Temujin’s grandson, Kublai, was beginning the conquest of Song China. Nobody had been able to stop them: even the feared Turkish horse archers and the highly skilled Persian fortress builders had fallen in front of them with frightening ease.
In spite of their supposedly wild nature, the Mongols proved to be moderate and good rulers. So good, in fact, the period between 1250 and 1350 is called Pax Mongolica, Mongolian Peace.
The Eurasian Steppe, for centuries the source of much trouble, was finally quiet. Trade flowed almost seamlessly from Zhongdu (modern day Beijing) to Europe. The aggressive Turks, who had been banging on Europe’s and Egypt’s doors, were defeated and their progress halted for a century.
While the political structure of Byzantium disintegrated (mostly due the lack of a capable leader like Leo III or Alexios Komnenos who could take advantage of the Turks’ weakness), economy flourished. Venetian and Genoese vessels cruised the waters of the Mediterranean loaded to the brim with Greek silks, Indian spices and Chinese porcelains. Factories in Corinth were working overtime to manufacture cloth, so much domestic supply of raw silk had to be supplemented by imports from the East. Despite squabbles, invasions and incursions, standards of living kept on increasing.
Then in 1347, disaster struck. Civil war broke out in Byzantine territories. And, even worse, the Black Death arrived. Nobody knew from certain where it originated but the first recorded outbreak, in 1332, literally decimated the Mongol ruling family in Xanadu, accelerating the decomposition of the Mongol khanate and ending the Pax Mongolica.
While the Civil War was devastating, the Black Death was even worse. Historians have long debated how many people died because of it. It hit the whole civilized world worse than nomadic people: one of the reasons the Turks were able to punch such a formidable hole in Europe’s defenses in the XV century is because they had suffered comparatively little from the plague while their Greek, Serbian and Bulgarian rivals had been hit very hard by it.
The effects were absolutely devastating: despite having recovered their dominating position in the Eastern Mediterranean after defeating the Genoese in 1380, Venetians became worried about the failing industrial and agricultural output of what was left of Byzantium (not to mention their own “colonies”), so worried they strengthened their ties with the Mameluke rulers of Egypt to make up for the lost output. Equally worrisome for them was the drop in demand of Eastern wares from Europe (it didn’t pick up again until the mid XV century), though much reduced Genoese competition partly made up for the difference.
The final decades of Byzantium were a long, pathetic decay. Timur’s victory over the Turks at Ankara in 1402 probably bought Byzantium a couple extra decades of life but only delayed the inevitable.
Then in 1453, the curtain fell together with the Theodosian walls under Mehmed II’s siege train.
However Byzantium’s legacy lived on: Venice was her linear descendant (despite having embraced a different brand of Christianity) and Russia, after emerging form the Mongol domination, claimed Byzantium’s legacy, so much her rulers wore a crown which bore the name of one Byzantium’s most illustrious families, the Monomakh’s Cap. 
 Much has been written about the Battle of Yarmuk (636). One point, however, should be made clear: the Arabs led by Rashidun (Rightly Guided Caliph) Umar ibn al-Khattar were much less numerous than the Byzantine troops confronting them. The immense hordes of Islam which overrun the Middle East are the product of later propagandists. Muslim Arabs managed to bring down Persia and almost crush Byzantium with relatively small numbers of well disciplined and highly motivated warriors. The reasons are very simple: both Empires were exhausted by two decades of war and a devastating plague outbreak, their armies were demoralized, disorganized, badly trained and equipped and, in Byzantium’s case, religious divisions helped insure there was no serious opposition to the Arabs in some areas.
 The early history of Byzantium was marked by continuous outbreaks of religious persecution, mimicking what happened in the Late Roman Empire. While Iconoclasm is the best known, it was small fries compared to what “heretics” such as the Montanists and the Monophysites had to endure.
 This is an extremely interesting topic I sadly lack the time to fully explore. Early Christianity had an extremely strong ideological stance against “money making”, a common characteristic to all Chiliastic movements (those expecting the End of Time in the immediate future). As Christianity evolved into a more sophisticated religion, this opposition weakened though in some denominations it remains strong, at least in name, to this day.
 The Magyar Confederation was the direct ancestor of modern day Hungary. The last of the Steppe People to settle in Europe (Mongols didn’t stick around for long after defeating the Poles and the Hungarians), they absorbed the remains of the Avars and became a formidable menace to Europe. They were fantastic horsemen and, as most Steppe People, hungry for loot and capable of incredible feats of mobility: in 942 they cut through Lombardy, Provence, Burgundy and sacked the Cordoba Caliphate and Andalusia.
 Manuel suffered a catastrophic defeat at the hands of the Seljuk Turks at Myriokephalon in 1176. All historians agree he had mobilized an enormous army, augmented by large numbers of Serbian and Hungarian mercenaries, to retake the Anatolian interior from the Turks. By ignoring all of the tenets laid down in military treatises to fight the highly skilled and mobile Turks, he marched his army right into an ambush. While the highly trained Byzantine cavalry, the skilled Hungarian horse archers and the heavily armored Serbian knights survived relatively unscathed, he lost the better part of his infantry and all his siege train. Worst of all, the expedition has been estimated at having cost well over a million nomismata, an immense sum squandered to obtain absolutely nothing. Had Manuel not walked into that ambush, history would have been very different as his army had all the means to crush the Seljuk Turks in a pitched battle and take their stronghold of Iconium.
 The Monomakh’s Cap was used to crown all Grand Princes and Tzars of Russia from the early XIV century up to 1721, when Peter the Great (r. 1682-1725) replaced it with the Imperial Crown of Russia. While it’s obviously of Asian origins (most likely Mongol), Russian propaganda associated it with Vladimir II Monomakh, Grand Prince of Kiev (r. 1113-1125), saying it has been sent as gift from Byzantium by his grandfather, Emperor Constantine IX (r. 1042-1055), scion of the illustrious Monomakhoi family.
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Hughes, Ian, Belisarius, 2009, Barnsley, Pen and Sword Books
Laiou, Anheliki E., Morrisson, Cécile, The Byzantine Economy, 2007, Cambridge, Cambridge University Press
Mango, Cyril (editor), The Oxford History of Byzantium, 2002, Oxford, Oxford University Press
McGeer, Eric, Sowing the Dragon’s Teeth, 2008, Washington DC, Dumbarton Oaks
Norwich, John Julius, Byzantium, 1990, London, Penguin Books
Weatherford, Jack, Genghis Khan and the Making of the Modern World, 2004, New York, Three Rivers Press