N'abalị mbụ n'ọnwa Septemba n'afọ 1939, ndị Nazi nke Jamanị weghaara Poland ma malite Agha Ụwa nke Abụọ. Na September 17, 1939, USSR, n'ikwekọ n'usoro iwu nzuzo nke Molotov-Ribbentrop Pact, wakporo Poland site n'ebe ọwụwa anyanwụ. N'ime ọnwa ole na ole, mba Sọviet Yuniọn malitere ịlụso mba Finland agha
Ọ dị mma. N'ihi agha a, a manyere Finland ịhapụ ókèala, gụnyere akụkụ nke Ógbè Viipuri, na Soviet Union na Nkwekọrịta Udo Moscow na mbido 1940. Finland tụfuru ókèala okike ya n'akụkụ Osimiri Rajajoki () n'ebe ndịda. 22,973 km2, ma ọ bụ 71.5 pasent nke ógbè dị na Karelian Isthmus, gụnyere obodo Viipuri na Sortavala, ghọrọ akụkụ nke Karelo-Finnish SSR e guzobere ọhụrụ na Soviet Union. Mgbe e mesịrị nkwekọrịta udo ahụ, a kpọpụrụ ndị nile bi n'ókèala ndị ahụ e nyefere, ihe karịrị narị puku mmadụ anọ, gaa n'etiti Finland.