From the 13th century , the two main Balkan powers Byzantium and Bulgaria fell Motion_directional victims to a process of decentralization , as local feudal lords grew Expansion stronger and more independent from the emperors in Constantinople and Tarnovo .

During the civil war in Byzantium in 1320s and 1330s , the Serbs conquered Conquering most of the Bulgarian and Aromanian populated Macedonia from the Byzantines .

In addition to the mainly Orthodox countries such as Bulgaria , Byzantium and Serbia , there were a number of Catholic possessions to the west and south held Defending by Venice , Genoa and the Kingdom of Hungary as well as Kingdom of Bosnia whose Bosnian Church ( closely related to the Bogomils ) was considered heretic by both Orthodox and Catholics .

During the civil war in Byzantium both Palaiologos and Kantakouzenos were trying to find external allies and used Using foreign mercenaries .

Probably the first local ruler to become aware of the impending Ottoman threat , Momchil unsuccessfully pleaded Request with the emperors of Bulgaria and Byzantium for help Assistance .

During the Byzantine civil wars Ivan Alexander regained Recovering control Control over several towns in Thrace and the Rhodopes but his frequent interference in the internal affairs of Byzantium hampered Hindering any closer relations between the two counties despite the peace established Building in 1332 .

The Abbasids had launched Process_start a huge expedition Attack with two separate armies in retaliation for the Byzantine emperor Theophilos 's successes the previous year , and aimed Aiming to sack Destroying Amorion , one of Byzantium 's largest cities .

The defeat opened Process_start the way for the brutal sack Destroying of Amorion a few weeks later , one of the most serious blows Byzantium suffered Bodily_harm in the centuries-long Arab–Byzantine Wars Attack .

The legacy of the rebellion endured both in Bulgaria and in Byzantium .

Bulgaria lost Earnings_and_losses its independence and remained Presence subject to Byzantium for more than a century and a half , until 1185 .

Mu'tasim targeted Aiming Amorium , a Byzantine city in western Asia Minor ( modern Anatolia ) , because it was the birthplace of the ruling Byzantine dynasty and , at the time , one of Byzantium 's largest and most important cities .

The sack did not ultimately alter Change the balance of power , which was slowly shifting Change in Byzantium 's favour , but it thoroughly discredited Judgment_communication the theological doctrine of Iconoclasm , ardently supported Supporting by Theophilos .

The emergence Coming_to_be of Muslim Arabs from Arabia in the 630s resulted in Causation the rapid loss Earnings_and_losses of Byzantium 's southern provinces ( Syria and Egypt ) to the Arab Caliphate .

With the Magyar threat eliminated Removing , Simeon led his hosts south and routed Attack the Byzantine army in the battle Hostile_encounter of Boulgarophygon in the summer of 896 , which forced Causation Byzantium to agree Agree_or_refuse_to_act to the Bulgarian terms .

In addition to the natural gains of land , and wealth and manpower received Receiving from these victories , the Byzantines also inflicted Bodily_harm a psychological defeat Earnings_and_losses on their opponents by recapturing Conquering territory deemed holy and important to Christendom , in particular the city of Antioch—allowing Byzantium to hold Defending two of Christendoms ' five most important Patriarchs , those making up Becoming_a_member the Pentarchy .

And while Byzantium took Conquering large parts of Palestine , Jerusalem was left untouched and the ideological victory from the campaign was not as great as it could have been had Byzantium recaptured Conquering this fourth Patriarchal seat of Christendom .

And while Byzantium took Conquering large parts of Palestine , Jerusalem was left untouched and the ideological victory from the campaign was not as great as it could have been had Byzantium recaptured Conquering this fourth Patriarchal seat of Christendom .

In 340 BC Demosthenes convinced Convincing the Athenian assembly to sanction Revenge action against Philip 's territories and to ally with the Achaemenids in Byzantium , which Philip was besieging Besieging .