The Fortress of Rumeli Hisarı, located on the European shore of the Bosphorus and in the northernmost district of Istanbul, is a striking monument.
Every year, hundreds of thousands of visitors to this great city follow the long-established tradition of taking a Bosphorus cruise and see the impressive castle from afar. Few of them realise that the building played a role in the Siege and Fall of Constantinople in 1453 and that its very shape and details exemplify the historical developments that led to this world-changing event, the end of the Byzantine Empire after over a thousand years and the establishment of the Ottoman Empire as a major player for five centuries.
Distinguished by its historical significance, its highly scenic setting overlooking the Fatih Sultan Bridge that links Europe and Asia, and its sheer monumentality, the site includes remains of the fortification walls with towers and gates as well as cisterns, fountains and a mosque. It currently functions as a cultural centre with an open-air theatre and a museum, set within the lower part of the recently built Bosphorus University Campus. In a city where there is so much to visit and discover – Byzantine churches, walls and cisterns, Ottoman palaces and mosques, bazaars, food and spices – and at a place where East meets West, Rumeli Hisarı Fortress is an off-the-beaten-track site, rarely listed among the “Top 10” or “Top 30 things to do and see”. Notwithstanding that lack of fame, it is a highlight on our Exploring Istanbul tour. We spend a day exploring the Bosphorus and its shores by private cruise and by bus, on an itinerary that has been carefully designed in order to include the fortress and unveil the Bosphorus straits and with them the city’s geostrategic significance.
The name Rumeli Hisarı, meaning “Fortress in the land of the Romans”, i.e. on the European or Byzantine side of the Bosphorus, is an afterthought. Initially, it was called Boğazkesen Castle, literally the “Throat Cutter”, as its purpose was to cut the straits – or the throat – that is the Bosphorus. It was built in 1452 by the order of Fatih Sultan Mehmed, famous as Mehmed the Conqueror or simply Mehmed II, by the narrowest point of the Bosphorus channel, just opposite Anadolu Hisarı – another Ottoman fortress located on the Anatolian side and constructed about 60 years earlier (1390-1395) as an observation post and safe point for a small number of Ottoman troops.
Despite damages, repairs and modifications throughout the centuries, Rumeli Hisarı still breathes history - its great significance lies in some specific and well-defined elements, closely related with the general circumstances and innovations that shaped the history of the Late Middle Ages and the pivotal events it was involved in. At the outset, however, two general points about castles and fortifications should be noted. First, it is important to keep in mind that talking about castles always means engaging with the topic of warfare and of the foreign and defence policies of states, no matter what period. Second, the development of medieval castles followed the military developments and standards of their period. This applies to all of the major functions of castles, namely serving as a) military fortresses b) as seats of local rulers, or c) as residential areas for the an area's entire population, or d) as a combination of those options.
The 15th century was that crucial time when the introduction of new materials (gunpowder) and new fighting techniques (firearms and complex siege machinery) led to dramatic changes affecting the conduct of warfare as well as the design of new fortresses. Hence, Rumeli Hisarı’s significance is due to some new features of military architecture, underlining the development of warfare technology at this fleeting but pivotal point in time, together with its contribution to the evolution of the developing Ottoman military. A further factor of significance is certainly the fortress’s key strategic location and its function during the Ottoman conquest, the final fall of Constantinople and the entire 11-century-old Byzantine Empire.
Numbers, new forms and new powerful technologies
Rumeli Hisarı occupies a total area of 30.000 square metres (ca. 7.4 acres) and really looks more like a small walled town dominating the sea. The walls enclose an irregular, roughly rectangular area, its shape determined by the lie of the land. They include three large towers (two on the andward side and one by the shore) and thirteen small watchtowers of different shapes placed along the walls between the main towers. The major tower in the north takes the form of a 28m (92ft) high 9-storey cylinder with a diameter of 23 (76ft).
A second big tower of the same shape and approximately the same size rises at the southern side. At the waterfront and in the middle of the seaward fortress wall stands the polygonal – 12-sided to be exact – Halil Pasha Tower, also 9 stories tall and with the same diameter. Conical wooden roofs covered with lead originally crowned these towers, as known for example from the very famous and impressive Galata Tower, built by the Crusaders around a century earlier. Three main gates placed next to the main towers offer access, while several smaller entrances and secret passages provided supplies to the arsenals and the food storage units.
All fortification walls and those of the towers are of 6 to 7m (19 to 23ft) thickness, corresponding to the needs created by the recent development of cannon technology. So, the width of the walls at Rumeli Hisarı was thrice that of the walls of Constantinople, which was 2.5 meters (8.2 ft).
The three huge towers, a major and typical element of Ottoman fortifications, in conjunction with the innovative emplacements for defensive cannons and the thick walls protecting the fortress against enemy guns, turned Rumeli Hisarı into a highly protected stronghold. This distinguishes it from the simpler and more old-fashioned Ottoman fortifications in the Balkans peninsula (e.g. in Albania, at Edirne and in Thrace).
Within half a century, the Ottomans had developed the best and most massive cannons of their time: the new castle with its strong walls was to be used as the base point for Ottoman offensive attacks, whilst the cannon ball technology of the period proved too ineffective to destroy walls of such thickness.
The introduction of gunpowder and the spread of artillery in the second half of the 15th century created a revolution in all aspects of defensive and offensive warfare, affecting both weapons and fortifications. Clearly, the Republic of Venice and its expert architects and engineers played a leading role in the evolution of military defence architecture, especially in the Aegean. They introduced several innovations by adding new defensive structures to existing forts, widening the moats, increasing the thickness of the walls and of the wall-walks for the placement and movement of cannons. Thus, during the 16th century, the Venetians completely changed the preceding medieval castles by introducing strong, squat and angular bastions with several projections and sloping walls based on the system of “side-fire”- aiming to leave attackers exposed and unprotected.
The Ottomans were never as advanced as the Venetians and other Europeans in regard to their defensive architecture – thus, they suffered several defeats by the Venetians and the Knights of Rhodes, until they finally came to besiege their fortified cities. However, the situation at Constantinople in 1453 was different: here, the Ottomans had the upper hand in terms of both attack and defense. Their dominance in both regards was beyond question and moreover, the recovery of the Byzantine Empire was beyond the achievable or imaginable by this time - as we shall see.
It's the economy, stupid – Byzantine decline, Ottoman apogee and the giant bombards
Of course, such superiority should be seen in context the state of instability and crisis prevailing in Europe during the 14th century: general economic and trade issues, the Venetian-Genoese quarrels, the emergence of new trading centres in Egypt and, last but not least, the extensive monetary crisis of the Byzantine Empire.
For several scholars, the real final blow to Byzantium was caused long before 1453, namely by the Fourth Crusade of 1204. During that event, the empire’s treasuries had been plundered, so that in spite of the recapture of Constantinople by the Byzantines in 1261, the Byzantine state was never able to recover. As a matter of fact, many political and financial problems continued to torment Byzantium even after 1261. From the middle of the 14th century until the final sack and collapse in 1453, civil wars, the plague and demographic issues, high taxation and a series of chronically misguided geopolitical and economic measures disrupted the formerly balanced fiscal cycle of the empire. The accumulation of Byzantine capital in the hands of major landowners and few private individuals had further adverse effects, since a great part of it was invested in Italian trade companies and institutions. Additionally, the financial importance and prestige of Constantinople was challenged harshly and decisively by the Ottoman expansion in the Balkans and Asia Minor and the consequent long-term recalibration of trade networks in the Eastern Mediterranean.
Under these circumstances, the fall of Constantinople was only a matter of time. The mid-15th century was the appropriate time for the ascendant Ottoman power to enter the city and provide a suitable capital for its new Empire. Mehmed II was clearly the key figure of his period, not only because he changed the Ottoman Sultanate into an Empire, but also because he transformed the previously prevalent lightly armoured cavalry into a centralized armed force with several different infantry corps. His leadership along with the excellent military machine that he created and the capacities of the new artillery batteries devastated the walls of Constantinople and likewise the moral of the Byzantines. We know that one of the most important deficiencies of the earlier unsuccessful Ottoman siege of Constantinople (1422) had been a lack of heavy cannons. To this extent, the new huge cannons, those giant bombards, were among the big winners of the final 1453 siege.
The fortress, the sea and the cannons at the final siege
By the time of Mehmed II, Constantinople was surrounded on all sides by Ottoman territories: the new Sultan with his reformed army made his military preparations in his European capital, Edirne in Eastern Thrace. In 1452 he ordered the casting of new massive bronze cannons by Orban, the same master-craftsman and engineer who earlier had unsuccessfully approached the Byzantine Emperor in order to promote and sell his new superguns. Bronze cannons were, however, extremely expensive and thus unobtainable for the Byzantine state, whereas for Mehmed II they were the most extraordinarily well-suited weapons to destroy his enemy. The biggest of Orban’s monster guns, famed as the “Royal Cannon”, was made of solid bronze, 8.2m (27ft) long, with a diameter of 76cm (30?).
It was at that very time that Mehmed II decided to construct Rumeli Hisarı on the European shore – in order for it and its older counterpart on the Asian side to block all sea traffic to and from the Black Sea and to protect a series of smaller fortresses further inland which were ready to accept his new large cannons. Rumeli Hisarı’ first saw action in November 1452, when its guns opened fire on a pair of Venetian ships attempting to escape the scene.
Ironically, the monster cannon of Mehmed II turned out to be of limited use in destroying the city’s walls: eventually, its immobility and slow rate rendered it ineffective. The final resolution came, after several weeks of stalling, via the sea and through assaults by smaller but still massive cannons.
The Bosphorus was very well protected by Rumeli Hisarı and the smaller sea fortresses and thus blocked that sea route for the Byzantines and any external force. The Ottomans vessels, under the protection of the new cannon artillery, forced the Byzantine fleet to find refuge away from the sea walls, while at the same time the Ottoman army devised a brilliant trick to penetrate into the heart of the city, an intriguing anecdote from the 1453 siege (a topic to which we will surely return in a future post). From that time onwards, the Ottoman bombarded the city walls continuously and from all sides. The local population was exhausted, the numerous cracks in the walls could not be restored any longer and Constantinople fell after a bloody and dramatic siege on 29 May 1453.
In conclusion, Rumeli Hisarı is indeed a place of great significance; a key structure standing in between two worlds during 1453, involved in inaugurating a new historical era and new international geopolitical balances that turned Constantinople for the second time in its long history into the capital of a newly-risen powerful Empire that was to be a major power for many centuries. It’s a perfect site to imagine the sounds, smells and images of battle, and to discover the Ottoman history and archaeology of Istanbul on our 1-week Exploring Istanbul tour, alongside with various gems from the Hellenistic, Roman, Byzantine and Ottoman world, hamams, bazaars and aromas of a city that has always straddled the edge of two continents and two worlds.