The Eastern Roman Empire lasted in one form or another more than 1,000 years longer than the Western Roman Empire. Rome was sacked by the Visigoths in 410 CE; Constantinople fell to the Ottomans in 1453 CE. Gibbon’s elegant denigration of the Byzantines long made it difficult to properly appreciate their survival in the face of challenges even more severe than those of the West.
The longevity of the Byzantine state is doubtless due primarily to the East’s more developed economy and several fundamental administrative and land reforms undertaken from the mid-7th through the 11th centuries. The brilliant defensive siting of their capital city also played a significant role in assuring the continuance of the Empire.
Military practices were also important, including flamethrowers delivering Greek Fire, which ignited on contact with water, and the heavily armored cavalry known as cataphracts, similar to the mounted forces of many of the Byzantines’ enemies to the east. Cataphracts deeply influenced the development of Western Europe’s feudal knights.
The defensive fortifications often referred to as the land walls of Theodosius, begun in the 5th Century and frequently repaired and upgraded to the 15th, were also crucial to the longevity of the Eastern Empire. They frustrated sieges by Persians, Arabs, Avars, Bulgars, Rus, and Turks among others. As long as the Byzantines controlled the seas, and the land walls held, Constantinople was impregnable.
The Fourth Crusade’s attack on Constantinople in 1204 succeeded in taking the city. This was largely due to loss of control of the seas to the Venetians. After this disaster, Byzantium was a hollow shell, with West European traders impoverishing the lands, peoples, and government of the remains of the Empire. The Fourth Crusade, mercilessly manipulated to their own advantage by the Venetians, is arguably the most effective and destructive commercial coup of all time. It took the remnants of the Eastern Empire until 1261 to win Constantinople back.
In the early 1450s, Sultan Mehmet II planned yet another Turkish attack on Constantinople. The forces of the Imperial City were led by Constantine XI, a brave and seasoned fighter.
Mehmet had fostered the development of a Turkish naval force, and had adopted the relatively primitive artillery of the times with enthusiasm. Advances in gunpowder formulation and barrel casting practices since the 1420s, when cannon were first used against Constantinople’s fortifications, meant that the threat posed to the land walls by artillery could no longer be dismissed. The Ottoman breaching of the Byzantine six-mile wall across the Isthmus of Corinth in December of 1446 served notice of the very real new threat cannon posed to the land walls of Constantinople.
This brings us to a person key to the chain of events that lead to the fall of Constantinople: Orban [or Urban], an engineer expert in casting cannons who appears to have arrived on the scene sometime shortly before or early in 1452. He seems to have come from a section of Hungary that is now part of Romania, and is sometimes argued to be of ethnically Wallachian or German background.
Orban offered his services to the Byzantines. Constantine arranged a tiny stipend to keep Orban in Constantinople, but even this pittance was not paid regularly. In 1452 Orban left for Edirne, where he was generously received by Mehmet. He offered to cast a supergun for the Ottomans, but claimed he did not know how to fire such a fieldpiece, which could be a dangerous procedure, as cannon barrels frequently ruptured.
Mehmet assured Orban that he had resources to fire any gun Orban could make, and an agreement was quickly achieved. Within 3 months Orban had cast a cannon used to command the Bosporus [November 1452].
Mehmet, well pleased, ordered a supergun and complementary long barreled cannons capable of breaching Constantinople’s land walls. These were cast in Edirne and laboriously transported roughly 150 miles [240 km]to the Ottoman siege lines, where they were installed and ready to commence bombardment by April 12. Mehmet had a total of about 70 field guns at Constantinople, and facilities to repair and cast new barrels on site if necessary. His army was unusual its ability to maintain and cast cannons in the field.
The barrel of the biggest of Orban’s guns cracked after several days of firing. It was repaired, only to rupture again, sending out deadly shrapnel. Christian sources claimed Orban lost his life when the gun barrel exploded, but there is evidence to suggest that this was a pious legend rather than historic fact.
A triangular targeting strategy ascribed to a Hungarian visitor to Mehmet’s camp resulted in efficient demolition of sections of Constantinople’s land walls. On April 18 Mehmet ordered an assault, which was repulsed. A subsequent defeat of Ottoman galleys enhanced the morale of the city’s defenders, until the Turks portaged galleys into the inadequately guarded waters of the Horn.
The siege was tightened. By the time of the final assault, May 29 1453, the Turks’ big guns had been bombarding the walls for forty-seven days, creating nine substantial breaches.
Constantine was lost in the melee. Mehmet became legendary with the victory. And a section of Constantinople became known as Gunner Verban District shortly after the Ottoman takeover, suggesting that the engineer and cannon maker may have taken up residence in the city he had offered to defend before turning to the Sultan for a job.
Refugee scholars fleeing the Ottoman takeover are often credited with accelerating and deepening the early Renaissance in Western Europe. More’s Utopians  indicated they had enough Latin books. What they really wanted was more information about the Greeks.
• Edward Gibbon’s The Decline and Fall of the Roman Empire may have been superseded with regard to certain points as history, but remains a masterpiece of vision, scholarship, and prose style. J. B. Bury’s annotations and publications provide a useful balance to Gibbon’s prejudice against the Eastern Roman Empire.
• Romilly Jenkins’ Byzantium: The Imperial Centuries A.D. 610 – 1071 is a good introduction to the Eastern Empire’s period of greatness. John Julian Norwich’s trilogy [Byzantium: The Early Centuries; Byzantium: The Apogee; and Byzantium: The Decline and Fall] provides a narrative history with scope and specifics.
• The Fourth Crusade is dealt with in detail in Donald Queller and Thomas Madden’s The Fourth Crusade: The Conquest of Constantinople [Second Edition]. Ernie Bradford’s The Great Betrayal: The Story of the Fourth Crusade is a useful narrative summary of events.
• Steven Runciman’s classic account of The Fall of Constantinople not only deals with the context and events of the military conquest, but also points to the effect of refugee scholars on the Renaissance in Western Europe. Roger Crowley’s 1453: The Holy War for Constantinople and the Clash of Islam and the West is a briskly paced narrative.