Rubuta ci gaba don wannan sakin layi - Babban ɗan Ferdinand I, Boris ya hau gadon sarauta bayan mahaifinsa ya yi watsi da shi sakamakon rashin nasarar Bulgaria a Yaƙin Duniya na I. A karkashin Yarjejeniyar Neuilly ta 1919, an tilasta Bulgaria, a tsakanin sauran abubuwa, ta ba da yankuna daban-daban, ta biya diyya ta yaƙi, kuma ta rage girman sojojinta. A wannan shekarar, Aleksandar Stamboliyski na agrarian Bulgarian Agrarian National Union ya zama firaminista. Bayan an hambarar da Stamboliyski a cikin juyin mulki a 1923, Boris ya amince da sabuwar gwamnatin Aleksandar Tsankov, wanda ya danne Jam'iyyar Kwaminisanci ta Bulgaria kuma ya jagoranci al'ummar ta ta wani ɗan gajeren yaƙin kan iyaka da Girka. An cire Tsankov daga mulki a 1926, kuma jerin firaministoci sun biyo baya har zuwa 1934, lokacin da ƙungiyar "Zveno" ta kafa juyin mulki
kuma ya haramta dukkan jam'iyyun siyasa. Boris ya yi adawa da gwamnatin "Zveno" kuma ya hambarar da su a cikin 1935, daga ƙarshe ya sanya Georgi Kyoseivanov a matsayin firaminista. Ga ragowar mulkinsa, Boris zai yi mulki a matsayin "a zahiri" mai cikakken mulki, tare da firaministocinsa galibi suna miƙa wuya ga nufinsa.