Byzantine – Ottoman Wars The Byzantine – Ottoman Wars were a series of decisive conflicts between the Ottoman Turks and the Byzantines that led to the final destruction of the Byzantine Empire and the rise of the Ottoman Empire . In 1204 the Byzantine capital of Constantinople was sacked and occupied by the Fourth Crusade rs , an important moment of the Christian East – West Schism . The Byzantine Empire , already weakened by misrule , was left divided and in chaos . Taking advantage of the situation , the Sultanate of Rum began seizing territory in Western Asia Minor until the Nicaean Empire was able to repulse the Seljuk Turks against the remaining territories still under Roman rule . Eventually Constantinople was re - taken from the Latin Empire in 1261 by the Nicaean Empire . However the position of the Byzantine Empire in the European continent remained uncertain due to the presence of the rival kingdoms of the Despotate of Epirus , Serbia and the Second Bulgarian Empire . This , combined with the reduced power of the Sultanate of Rum ( Byzantium ' s chief rival in Asia ) led to the removal of troops from Asia Minor to maintain Byzantium ' s grip on Thrace . However the weakening of the Sultanate of Rum was by no means a blessing to the Empire as nobles known as " ghazis " began setting up their fiefdoms , at the expense of the Byzantine Empire . While many Turkish beys participated in the conquest of Byzantine and Seljuk territory , the territories under the control of one such Bey named Osman I posed the greatest threat to Nicaea and to Constantinople . By 1299 , Osman I felt assured of his position to declare himself Sultan and thereafter his territories became known as the Ottoman Empire . Within 50 years of Osman I ' s establishment of the Ottoman beylik , Byzantine Asia Minor had ceased to exist and by ca . 1380 , Byzantine Thrace was lost to the Ottomans . By ca . 1400 , the once mighty Byzantine Empire was nothing more than a collection of the Despotate of the Morea , a few Aegean islands and a strip of land in Thrace in the immediate vicinity of the Capital . The Crusade of Nicopolis in 1396 , Timur ' s invasion in 1402 and the final Crusade of Varna in 1444 allowed a ruined Constantinople to stave off defeat until 1453 . With the conclusion of the war Ottoman supremacy became established in the eastern Mediterranean . Origins of the war . Following the Byzantine – Seljuk Wars , the various Turks that had settled in Asia Minor had begun to carve out several beyliks or semi - independent states for themselves following the collapse of the Sultanate of Rum in the late 13th century . One of the Nobles ( Bey ) of the old Sultanate was Osman I , also known as Uc beg or " protector " . Osman ' s domain was in the north west region of Anatolia , not far from Constantinople . Consequently the proximity to the Byzantine Empire allowed Osman and his " ghazi " raiders to fully exploit the weakened position that the Byzantines were at in the late 13th century . This low ebb was due in part to Michael Palaeologus ' ambitions of driving out the Latins from Greece ; the transfer of troops from Asia Minor to Greece opened Asia Minor to attack . Rise of the Ottomans : 1265 – 1328 . Following Michael VIII Palaeologus ' reconquest of Constantinople in 1261 , the Byzantine Empire was left in a grave position . There was plenty of talk among the Latin states of the Greek mainland and other regions of retaking Constantinople for the Latin Empire whilst to the north the main threat came from Serbian expansion into the Balkans by king Stephen Uros . What was once a strong frontier under the Komnenian dynasty at the Danube river now threatened Constantinople itself . To solve these problems Michael Palaeologus began consolidating his rule ; he had the younger co - emperor John IV blinded , which resulted in much resentment . To counter this , the Byzantine Emperor installed a new Patriarch of Constantinople , Germanus III , ordering him to lift an excommunication that had been placed against him by the former Patriarch Arsenios Autoreianos and to submit to the authority of Rome in order to alleviate the Latin threat . As the Byzantine Empire continued the conquest of Latin territory , the Turks under Osman I began their raids into Byzantine Anatolia ; Sogut and Eskisehir were taken in 1265 and 1289 respectively . Michael Palaeologus was unable to deal with these early setbacks due to the need to transfer troops to the West . In 1282 , Michael Palaeologus died and his son Andronicus II took power . The death of the old Byzantine Emperor came as a relief for the society at large ; his policy of Latin appeasement to the Church in Rome , heavy taxation and military expenditure placed a severe burden on the people . As the Ottoman Turks began taking land from the Empire , they were seen as liberators of Anatolians and many soon converted to Islam undermining the Byzantine ' s Orthodox power base . Andronicus ' rule was marked with incompetence and short - sighted decisions that in the long run would ruin the Byzantine Empire beyond repair . He began to debase the Byzantine " hyperpyron " , resulting in a reduction of the value of the Byzantine economy ; taxes were decreased and instead placed upon the Knight - class " Pronoia " . To popularize his rule he repudiated the union of the Orthodox and Catholic Churches decreed by the Second Council of Lyon in 1274 , thereby further increasing hostilities between the Latins and the Byzantines . Andronicus II took a deep interest in preserving the Anatolian lands of Byzantium and ordered construction of forts in Asia Minor and vigorous training of the army . The Byzantine Emperor ordered that his court be moved to Anatolia to oversee the campaigns there and instructed his General Alexios Philanthropenos to push back the Turks . Early successes were rendered useless when Alexios staged an unsuccessful coup , leading to his blinding and the end of his campaigns . This allowed the Ottomans to lay siege to Nicaea in 1301 . A further defeat on Andronicus ' son Michael IX and the Byzantine general George Mouzalon occurred at Magnesia and Bapheus in 1302 . Despite this , Andronicus tried once more to strike a decisive blow back at the Turks , this time hiring Catalan mercenaries . Under the guidance of Michael IX and the leadership of Roger de Flor , the 6 , 500 - strong Catalan Company in the spring and summer of 1303 to drive back the Turks . The mercenaries ' expensive services drove them back from Philadelphia to Cyzicus and in doing so brought great destruction to the Anatolian landscape . Once again these gains were thwarted by internal matters . Roger de Flor was assassinated and , in revenge , his company began pillaging the Anatolian countryside . When they finally left in 1307 to attack Byzantine Thrace , the locals welcomed the Ottomans who once again began blockading key fortresses in Asia Minor . The Ottomans were able to implement their military success due to the numerous divisions amongst their opponents . Many of the peasant classes in Anatolia saw the Ottomans as the better master . After these defeats , Andronicus was in no position to send many troops . In 1320 , Andronicus II ' s grandson , Andronicus III , was disinherited following the death of his father , Michael IX , the Emperor ' s son and heir apparent . The following year , Andronicus III retaliated by marching on Constantinople and was given Thrace as an appanage . He kept on pressing for his inheritance and , in 1322 , was made co - emperor . This culminated into a small scale Balkan war in which Serbia backed Andronicus II and the Bulgarians backed his grandson . Eventually Andronicus III emerged triumphant on May 23 , 1328 . As Andronicus III consolidated his hold on Byzantium , the Ottomans succeeded in taking Bursa from the Byzantines in 1326 . Byzantium counter : 1328 – 1341 . Andronicus III ' s reign was to be marked by Byzantium ' s last genuine and promising attempt at restoring " the glory that was once Rome " . In 1329 , Byzantine troops were sent to meet the Ottoman forces who had been blockading , and in effect laying siege to , Nicaea since 1301 . Byzantine counter - attacks coupled with the scale of Nicaea ' s defenses had frustrated the Ottomans ' attempts at taking any cities . The fate of Nicaea was sealed when the Byzantine relief army was defeated at Pelekanos on 10 June 1329 . In 1331 , Nicaea surrendered , resulting in a massive blow considering that it was the capital of the Empire 70 years prior . Once again the Byzantines ' military power was depleted and Andronicus III was forced into diplomacy as his grandfather was before him ; in return for the safety of the remaining Byzantine settlements in Asia Minor , tribute would be paid to the Ottomans . Unfortunately for the Byzantine Empire , this did not stop the Ottomans from laying siege to Nicomedia in 1333 ; the city finally fell in 1337 . Despite these setbacks , Andronicus III was able to score a few successes against his opponents in Greece and Asia Minor ; Epirus along with Thessalonika were subjugated . In 1329 , the Byzantines captured Chios and , in 1335 , secured Lesbos . Nonetheless , these isolated Islands were isolated exceptions to the general trend of increasing Ottoman conquests . Furthermore , none of the Islands were a part of the Ottoman domain ; their capture demonstrates the potential that the Byzantines had at the time of Andronicus III . Byzantine military ability would be further weakened by Serbian expansions into recent acquisitions by Andronicus III ( Epirus ) and finally by a devastating civil war that would subjugate the Byzantine Empire as a vassal to the Ottomans . Balkan invasion and civil war : 1341 – 1371 . Andronicus III died in 1341 leaving his 10 year old son John V to rule . A regency was set up with John Cantacuzenus , the young Emperor ' s mother , Anna of Savoy , and the Patriarch John XIV Kalekas . Rivalries between Kalekas and Cantacuzenus led to a destructive civil war , in which Cantacuzenus emerged triumphant at Constantinople in February 1347 . During this time plague , earthquakes and Ottoman raiding continued until only Philadelphia remained in Byzantine hands and only so by payment of a tribute . Throughout the civil war the Byzantines on both sides employed Turks and Serbs with mercenaries pillaging at will , leaving much of Macedonia in ruin and in the hands of the newly - create Serbian Empire . Following this victory , Kantakouzenos ruled as co - emperor with John V . This dual rule eventually failed and the two waged a new civil war further diminishing what was left of Byzantium ' s integrity in the eyes of her troublesome neighbors . John VI Cantacuzenus emerged triumphant once again and replaced the now exiled John V Palaeologus with his son Matthew Cantacuzenus as junior co - emperor . However , the Turks , under Osman I ' s son , Orhan I , now came into play by capturing the fort of Kallipolis ( Gallipoli ) in 1354 and gaining access to the European mainland . The arrival of the seemingly unbeatable Ottoman soldiers surrounding Constantinople caused a panic in Constantinople , capitalized by John V who , with the assistance of the Genoese , staged a coup and ousted John VI Cantacuzenus in November 1354 . As a result , John VI would later become a monk . The civil war did not end there ; Matthew Cantacuzenus now obtained troops from Orhan and began a bid for taking Constantinople . His capture in 1356 ended his dreams of becoming Emperor and with it came an ephemeral defeat for the Ottomans who had favored the overthrow of John V . Following the end of the civil conflict came a small lull in fighting between the expanding Ottomans and Byzantines . In 1361 Didymoteichon fell to the Turks . Orhan ' s successor , Murad I was more concerned with his Anatolian positions . However , just like Alp Arslan of the Seljuk Turks , Murad I left the taking of Byzantine territory to his vassals with Philippopolis falling after major campaigning between 1363 – 4 and Adrianople succumbing to the Ottomans in 1369 . The Byzantine Empire was in no position to launch any decent counter - attack or defence of these lands ; by now the Ottomans had become supremely powerful . Murad I crushed an army of Serbians on 26 September 1371 at the Battle of Maritsa leading to the end of Serbian power . The Ottomans were now poised to conquer Constantinople . In an attempt to stave off defeat , John V appealed to the Pope for support offering submission to Rome in return for military support . Despite publicly confessing the Roman Catholic Faith in St . Peter ' s Basilica , John V received no help . John V therefore was forced to turn to reason with his enemies , the Ottomans . Murad I and John V then came to an agreement whereby Byzantium would provide regular tribute in troops and money in exchange for security . Byzantine civil war and vassalage : 1371 – 1394 . By now the Ottomans had essentially won the war ; Byzantium was reduced to a few settlements other than Constantinople and was forced to recognize its vassal status to the Ottoman Sultan . This vassalage continued until 1394 . However , whilst Constantinople had been neutralized , the surrounding Christian powers were still a threat to the Ottomans and Asia Minor was not under complete Ottoman control . The Ottomans continued their thrust into the Balkans , proving to be great conquerors in Europe as they were in Anatolia ; in 1385 Sofia was captured from the Bulgarians and Nis was taken the following year . Other smaller states were subjugated as vassals , including the Serbs . Serbian resistance was crushed at the Battle of Kosovo in 1389 , much of Bulgaria was taken in 1393 by Bayezid I ( the Thunderbolt ) and in 1396 the last bastion of Bulgarian independence was wiped out when Vin fell . Ottoman advances into the Balkans was aided by further Byzantine civil conflict — this time between John V Palaeologus and his eldest son Andronicus IV . With Ottoman aid from Murad I , John V was able to blind Andronikus IV and his son John VII Palaeologus in September 1373 . Andronicus escaped with his son and secured Murad ' s aid by promising a higher tribute than John V ' s . The civil strife continued as late as September 1390 though potential for conflict continued until 1408 . John V eventually forgave Andronicus IV and his son in 1381 , angering his second son and heir apparent , Manuel II Palaeologus . He seized Thessalonika , alarming the Ottoman Sultan in liberating parts of Greece from Ottoman rule . The death of Andronicus IV in 1385 and the capitulation of Thessalonika in 1387 to Hayreddin Pasha encouraged Manuel II Palaeologus to seek the forgiveness of the Sultan and John V . His increasingly close relationship with John V angered John VII who saw his right as the heir threatened . John VII launched a coup against John V but despite Ottoman and Genoese aid his reign lasted mere five months before he was toppled by Manuel II and his father . Fall of Philadelphia . Whilst the civil war was raging , the Turks in Anatolia took the opportunity to seize Philadelphia in 1390 , marking the end of Byzantine rule in Anatolia , although by now the city was far from Imperial rule . The city had long been under only nominal Imperial rule and its fall was of little strategic consequence to the Byzantines – whose Emperor had to suffer the humiliation of accompanying the Sultan during the campaign . Vassalage . Following John V ' s death , Manuel II Palaeologus was able to secure his throne and establish good relations with the Sultan , becoming his vassal . In return for Ottoman acceptance of his reign Manuel II was forced to dismantle the fortifications at the Golden Gate , something that he did not take lightly to . Resumption of hostilities : 1394 – 1424 . In 1394 , relations between the Byzantines and the Ottomans changed for the worse and the war between the two resumed when the Ottoman Sultan Bayezid ( ruled 1389 – 1402 ) ordered the execution of Manuel II after the Emperor attempted to reconcile his nephew John VII . The Ottoman Sultan then later changed his decision and demanded that a mosque and a Turkish colony be established in Constantinople . Manuel II not only refused this , he also refused to pay the Sultan tribute and went so far as to ignore the Sultan ' s messages , leading to a siege of the city in 1394 . Manuel II called for a Crusade , which came in 1396 . Under the future Holy Roman Emperor Sigismund , the Crusade was crushed at Nicopolis in 1396 . The defeat convinced Manuel II to escape the city and travel to Western Europe for aid . During this time the reconciled John VII led the city ' s successful defence against the Ottomans . The siege was finally broken when Timur of the Chagatai Mongols led an army into Anatolia , dismantling the network of beyliks loyal to the Ottoman Sultan . At the Battle of Ankara , Timur ' s forces routed Bayezid I ' s forces , a shocking defeat for which no one were prepared . In the aftermath , the Ottoman Turks began fighting each other led by Bayezid ' s sons . The Byzantines wasted no time exploiting the situation and signed a peace treaty with their Christian neighbours and with one of Bayezid ' s sons . By signing the treaty , they were able to recover Thessalonika and much of the Peloponnese . The Ottoman civil war ended in 1413 when Mehmed I , with the blessings of the Byzantine Empire , defeated his opponents . The rare amity established between the two states would not last ; the death of Mehmed I and the rise of Murad II in 1421 coupled with the ascent of John VIII to the Byzantine throne led to a deteriorated change in relations between the two . Neither leader was content with the status quo . John VIII made the first and foolish move by inciting a rebellion in the Ottoman Empire : a certain Mustafa had been released by the Byzantines and claimed that he was Bayezid ' s lost son . Despite the odds , a sizable force had mustered in Europe under his banner , defeating Murad II ' s subordinates . Murad II ' s furious reply eventually smashed this upstart and , in 1422 , began the Siege of Thessalonica and Constantinople . John VIII then turned to his aging father , Manuel II , for advice . The result was that he incited yet another rebellion in the Ottoman ranks — this time supporting Murad II brother ' s claim , Kucuk Mustafa . The seemingly promising rebellion had its origins in Asia Minor with Bursa coming under siege . After a failed assault on Constantinople , Murad II was forced to turn back his army and defeat Kucuk . With these defeats , the Byzantines were forced once more into vassalage — 300 , 000 coins of silver were to be delivered to the Sultan as tribute on an annual basis . Ottoman victory 1424 – 1453 . The Ottomans faced numerous opponents between 1424 and 1453 . Tied down by the siege of Thessalonika , the Ottomans had to contend with the Serbs under George Brankovic , the Hungarians under John Hunyadi and the Albanians under George Kastrioti Skanderbeg . This resistance culminated into the Crusade of Varna of 1444 , which , despite much local support and deception - a peace treaty was unilaterally revoked by the Hungarians - was defeated . In 1448 and 1451 , there was a change in the Byzantine and Ottoman leaderships , respectively . Murad II died and was succeeded by Mehmed the Conqueror whilst Constantine XI Palaiologos succeeded John VIII . Constantine XI and Mehmed did not get along well ; the former ' s successful conquests of Crusader territory in the Peloponnese alarmed the latter , who had since subjugated as vassals the crusaders in the region , and Mehmed had around 40 , 000 soldiers sent to nullify these gains . Constantine XI threatened to rebel against Mehmed unless certain conditions were met by the Sultan regarding the status quo . Mehmed responded to these threats by building fortifications in the Bosporus and thus closed Constantinople from outside naval assistance . The Ottomans already controlled the land around Constantinople and so they began an assault on the city on 6 April 1453 . Despite a union of the Catholic and Orthodox Churches , the Byzantines received no official aid from the Pope or Western Europe , with the exception of a few soldiers from Venice and Genoa . England and France were in the concluding stages of the Hundred Years War . The French did not wish to lose their advantage in the fight by sending knights and the English were in no position to do so . Spain was in the final stages of the Reconquista . The Holy Roman Empire , never centralized enough behind the Hohenstaufen to unite the principalities , had exhausted what could be spared at Varna . Further fighting among the German princes and the Hussite wars seriously reduced the willingness of most to perform a crusade . Poland and Hungary were key participants at Varna and the defeat there along with the Polish – Teutonic Wars kept them busy and unwilling for further commitments . Other than these major European powers , the only others were the Italian city - states . Genoa and Venice were both enemies of the Ottomans , but also of each other . The Venetians considered sending their fleet up to attack the fortifications guarding the Dardanelles and the Bosporus , thereby relieving the city but the force was too small and arrived too late . The Ottomans would have overpowered any military assistance provided by one city , even one as large and powerful as the Venetian Republic . In any case some 2 , 000 mercenaries , mostly Italian under Giovanni Giustiniani Longo , arrived to assist in the defence of the city . The city ' s entire defence fell to these mercenaries and 5 , 000 militia soldiers raised from a city whose population had been seriously eroded by heavy taxation , plague and civil conflict . Though poorly trained , the defenders were well armed in many weapons , except for any cannons to match the Ottoman ' s own artillery . The city ' s fall was not a result of the Ottoman artillery nor their naval supremacy ( many Italian ships were able to aid and then escape the city ) . The Fall came about due to the combined weight of overwhelming odds stacked against the city — outnumbered by more than 10 to 1 , the defenders were overcome by sheer attrition as well as the skill of the Ottoman Janissaries . As the Ottomans continued their seemingly unsuccessful and costly assaults , many in their camp began to doubt the success of the siege ; history had shown the city to be invincible to Ottoman siege and the memories of Ankara and Varna , even if they had not altered the status quo for long , lingered in their minds and in the minds of the hopeful defenders . In an effort to raise morale , the Sultan then made a speech reminding his troops of the vast wealth and pillaging of the city to come . An all - out assault captured the city on May 29 , 1453 . As the Ottomans fanned out to sack the city , their naval discipline began to collapse and many Genoans and Venetians escaped in vessels from the city , including Niccolò Barbaro , a Venetian surgeon present at the siege who wrote : After the siege , the Ottomans went on to take Morea in 1460 , and Trebizond in 1461 . With the fall of Trebizond came the end of the Roman Empire ; the Palaeologan dynasty continued to be recognized as the rightful emperors of Constantinople by the crowned heads of Europe until the 16th century when the Reformation , the Ottoman threat to Europe and decreased interest in crusading forced European powers to recognize the Ottoman Empire as masters of Anatolia and the Levant . Causes of the Byzantine defeat . Latin intervention . The Latin presence in the Balkans seriously undermined the Byzantines ' ability to coordinate their efforts against the Ottoman Turks . This is exemplified by Michael VIII Palaeologus , whose attempts to drive the Latins out of Greece led to the abandonment of the Anatolian borders which allowed several beyliks , as well as the Turks of Osman I to raid and settle former Byzantine lands . Andronicus II ' s campaigns in Anatolia , though it obtained some military success , was constantly thwarted by events in the west of the Empire . In any event , the Byzantines were forced to choose between Papal and Latin threat of attack or an unpopular union , which was exploited by numerous rival claimants as cause for a coup against the Byzantine Emperor . Nonetheless , towards the mid - and late - 14th century , the Byzantines began to receive nominal aid from the West . This was little more than sympathy toward a fellow - Christian power fighting a Muslim power and despite two Crusades , the Byzantines " received as much help from Rome as we did from the [ Mamluk ] sultan [ of Egypt ] . " The Mamluk Sultanate in 13th century had been one of the most determined powers to remove Christian influence in the Middle East and raiding by Cyprus did not change this in the 14th and 15th centuries . Byzantine weakness . Following the Fourth Crusade , the Byzantines were left in an unstable position . The capture of Constantinople in 1261 and subsequent campaigning did not come at a good time — the weakening of the Sultanate of Rum resulted in many beyliks breaking away as autonomous states , such as the Emirate founded by Osman I . Although this weakening of power gave the Empire of Nicaea a temporary free hand , it was nothing more than a small respite not capitalized as much as it could have been . In order to implement these Greek re - conquests , Michael VIII was forced to levy crushing taxes on the Anatolian peasantry in order to pay for the expensive army that modeled around the Komnenian army . This led to much peasant support for the Turks whose system resulted in fewer taxes initially . After Michael VIII ' s death , the Byzantines suffered from constant civil strife early on . The Ottomans suffered civil conflict as well , but this occurred much later on in the 15th century , by that time the Byzantines were too weak to reconquer much territory . This is in contrast to the civil strife of Byzantium , occurring at a time ( 1341 – 71 ) when the Ottomans were crossing into Europe through a devastated Gallipoli and surrounding the city , thus sealing its fate as a vassal . When attempts were made to break this vassalage , the Byzantines found themselves out - matched and at the mercy of Latin assistance , which despite two Crusades , ultimately amounted to nothing . Ottoman strengths . The Ottomans had great diplomatic skill and ability to raise vast numbers of troops . Initially , their raiding gave them great support from other Turks near Osman ' s small domain . In time however , as the Turks began to settle in land poorly defended by the Byzantines , they were able to exploit the hardships of the peasant classes by recruiting their aid . Those that did not assist the Ottomans were raided themselves . Eventually , the cities in Asia Minor , cut off from the outside surrendered and the Ottomans soon mastered the art of siege warfare . It was the Ottomans ' skill with dealing with their opponents that made them very powerful very quickly . They would subjugate their opponents as vassals rather than destroy them , otherwise they would have exhausted themselves in the process . The exacting of tribute from conquered states in the form of children and money was effective in forcing subjugation over conquest . Coupled with this , the entire region was composed of many states ( Bulgaria , Serbia , Latin states ) who would just as soon fight each other as the Ottomans and realized too late that the Ottoman forces defeated them by integrating them in a network of subordinate states . Consequences . The fall of Constantinople came as a shock to the papacy , which ordered an immediate counter - attack in the form of a crusade . Only Philip the Good , Duke of Burgundy responded but under the condition that a powerful monarch assist him ; however , none would do so . Pope Pius II then ordered another crusade . Again , no substantial efforts were seen by any of Europe ' s major leaders of the time . This forced the Pope himself to lead a crusade . His death in 1464 led to the disbanding of the crusade at the port of Ancona . The Fall also had many implications in Europe : the influx of Greek science and culture into Europe by those escaping the Ottomans was a crucial factor in catalyzing the European Renaissance . The failed attempts at defeating the Ottomans at Nicopolis and Varna , the loss of the Holy Land ( without Byzantium the Crusades could not re - supply en route ) and the lack of a genuine counter - attack led many , including Martin Luther , into believing that the Turks were God ' s punishment against the sins of Christians : " How shamefully . . . the pope has this long time baited us with the war against the Turks , taken our money , destroyed so many Christians and made so much mischief ! " Nonetheless , by 1529 , Europe began to rise to the threat of the Ottomans . Martin Luther , changing his views , wrote that the " Scourge of God " had to be fought with great vigour by secular leaders rather than as Crusades initiated by the Papacy . With the Ottomans ' hold on Constantinople " de facto " recognized by Europe ' s lack of action , the Ottomans went onto facilitate further conquests in Europe and in the Middle East . Their power finally reached a peak in the mid 17th century . Their success through the Janissaries became their new weakness ; conservative and extremely powerful , Ottoman reform was difficult to implement whilst European armies became increasingly more resourceful and modernized . As a result , Russian and Austrian attempts to contain the Ottoman threat became more and more a formality until the official dissolution of the Empire after World War I .