I muri i te 1938 "Anschluss" i waenganui i Germany me Austria, Yugoslavia faaite i te rohe ki te Reich Tuatoru, a ka i raro i te pēhanga nui haere rite ona hoa tata whakaritea ratou ki te Axis mana. I te Paenga-whāwhā o te tau 1939, ka whakatuwheratia e Itari he rohe tuarua me Yugoslavia i a ia e whakaeke ana, e noho ana i te whenua tata o Albania. I te tīmatanga o te Pakanga Tuarua o te Ao, ka kī te kāwanatanga o Yugoslavia i tōna tōrangapū. I waenganui i te Mahuru me te Noema 1940, ka uru a Hungary me Romania ki te Tiriti e toru, ka hono atu ki te Axis, a ka whakaekea a Itari ki Kariki
He aha? Mai i taua wā, kua tata katoa a Yugoslavia ki nga mana Axis me o ratou kaitautoko, a kua kaha tana tuakore ki te pakanga. I te mutunga o Hui-tanguru 1941, ka uru atu a Bulgaria ki te Pact. I te ra i muri mai, ka uru mai nga hoia Tiamana ki Bulgaria mai i Romania, ka kati i te mowhiti huri noa i Yugoslavia. I te whakaaro ki te whakarite i tana taha tonga mo te whakaeke tata ki te Soviet Union, ka tiimata a Adolf Hitler ki te akiaki i a Yugoslavia kia uru atu ki te Axis. I te 25 o Poutu-te-rangi 1941, i muri i te roa o te roa, i hainatia e te kawanatanga o Yugoslavia te Pact. E rua nga ra i muri mai, he roopu o nga rangatira o te Royal Yugoslav Air Force, i whakakorehia te rangatira o te whenua, a Prince Paul, i roto i te toto toto, i whakanohoia tana taina taiohi a Peter ki runga i te torona, a ka kawea mai ki te mana "te kawanatanga o te kotahitanga o te motu" i arahina e General Dušan Simović. I riri a Hitler, i whakahau tonu ia i te whakaekenga o te whenua, i timata i te 6 o Aperira 1941.