Barkewar yakin duniya na daya a shekara ta 1914 ya haifar da rarrabuwar kawuna a siyasar kasar ta Girka, inda sarki Constantine na daya mai sha'awar Jamus ya yi kira da a yi tsaka mai wuya yayin da firaminista Eleftherios Venizelos ya matsawa Girka ta shiga kawancen.Rikicin da ke tsakanin masarautu da ’yan Venize a wasu lokuta yakan haifar da yakin basasa kuma aka san shi da Schism na kasa.A cikin 1917, Allies sun tilasta Constantine ya yi murabus don goyon bayan dansa Alexander da Venizelos sun dawo a matsayin Firayim Minista.A karshen yakin, manyan kasashen duniya sun amince cewa birnin Smyrna (Izmir) na Ottoman da kuma yankinsa mai yawan al'ummar Girka, a mika shi ga kasar Girka.Sojojin Girka sun mamaye Smyrna a shekara ta 1919, kuma a shekara ta 1920 gwamnatin Ottoman ta sanya hannu kan Yarjejeniyar Sèvres;Yarjejeniyar ta tanadi cewa nan da shekaru biyar za a gudanar da taro a Smyrna kan ko yankin zai shiga Girka.Sai dai masu kishin kasa na Turkiyya karkashin jagorancin Mustafa Kemal Ataturk sun hambarar da gwamnatin Ottoman tare da shirya wani kamfen na soji kan sojojin Girka, wanda ya haifar da yakin Greco-Turkish (1919-1922).Wani babban filin farmaki na Girka ya tsaya a cikin 1921, kuma zuwa 1922 sojojin Girka sun koma baya.Dakarun Turkiyya sun sake kwace Smyrna a ranar 9 ga Satumban 1922, tare da cinnawa birnin wuta tare da kashe 'yan Girka da Armeniya da yawa.Yarjejeniyar Lausanne (1923) ce ta kawo karshen yakin, inda aka yi musayar al'umma tsakanin Girka da Turkiyya bisa tushen addini.Fiye da Kiristocin Orthodox miliyan daya ne suka bar Turkiyya don musayar Musulmai 400,000 daga Girka.Abubuwan da suka faru na 1919-1922 ana ɗaukarsu a Girka a matsayin lokacin bala'i na musamman na tarihi.Tsakanin 1914 zuwa 1923, an kiyasta cewa Girkawa daga 750,000 zuwa 900,000 ne suka mutu a hannun Turkawa Daular Usmaniyya, abin da masana da dama suka kira kisan kare dangi.