Kammala jumla mai zuwa: Mai nasara a cikin 1347, John VI Kantakouzenos ya yi mulki a matsayin co-emperor har sai dansa Matiyu Kantakouzenos ya kai hari ga John V a cikin 1352, wanda ya haifar da
yakin basasa na biyu. John V ya nemi mai mulkin Serbia, Stefan Dušan don taimako, kuma Dušan ya wajaba ta hanyar aikawa da mahayan dawakai 4,000 na Serbia don taimaka masa. Matiyu Kantakouzenos ya nemi taimakon mahaifinsa, kuma 'yan Turkawa Ottoman 10,000 sun bayyana a Demotika (Didymoteicho) a watan Oktoba na 1352 kuma sun yi yaƙi da sojojin abokan haɗin gwiwar John V na Serbia a fagen yaƙi wanda ya haifar da lalata abokan haɗin gwiwa da nasara ga Turkawa da yawa a cikin hidimar Byzantines. Da haka Daular Ottoman ta sami yankinta na farko na Turai, a Çimpe da Gallipoli. Zai iya sake ɗaukar Constantinople a cikin 1354, John V ya cire kuma ya yanke John VI Kantakouzenos; ta hanyar 1357, ya kuma sauke Matiyu, wanda Serbs suka kama kuma aka fanshe shi ga John V.