Whakaotihia te rerenga e whai ake nei: Ko te tama matamua a Ferdinand I, ko Boris i riro i te torona i te wehenga o tona papa i muri i te hinganga o Bulgaria i te Pakanga Tuatahi o te Ao. I raro i te 1919 Treaty o Neuilly, i akiakihia a Bulgaria, i roto i era atu mea, ki te tuku i nga rohe rereke, ki te utu i nga utu pakanga, me te whakaheke i te rahi o tana ope taua. I taua tau ano, ko Aleksandar Stamboliyski o te agrarian Bulgarian Agrarian National Union i riro hei perehimana. Whai muri i te whakakorenga o Stamboliyski i roto i te whakapae i te tau 1923, i mohio a Boris ki te kawanatanga hou a Aleksandar Tsankov, nana i tino tukino te Rōpū Communist Bulgarian me te arahi i te iwi i roto i te pakanga rohe poto me Kariki. I nekehia atu a Tsankov i te mana i te tau 1926, ā, ka whai ake he raupapa o ngā Pirimia tae noa ki te tau 1934, i te wā i whakatūria ai e te kaupapa "Zveno"
i whakatūria ai ngā rōpū tōrangapū katoa. I whakahe a Boris ki te kawanatanga "Zveno" a ka hinga i a raatau i te 1935, i te mutunga ka whakauruhia a Georgi Kyoseivanov hei perehitini. Mo te toenga o tana kingitanga, ka noho a Boris hei "de facto" rangatira tino nui, me ana rangatira rangatira e tuku ana ki tana hiahia.