 Kuputika kweHondo yeNyika II, uye zvikurukuru kupinda kweGermany nechisimba muNorway, zvakaita kuti Grieg arambe mitemo yaStalin. Muna 1939, Soviet Union yakasaina Chibvumirano cheMolotov-Ribbentrop neGermany yeNazi uye, kutozosvikira pakupinda kweNazi muna 1941, akarayira vaKomonisiti munyika yose kurangarira hondo iri kuitika sehondo yeUshe umo ivo havafaniri kutora rutivi. Grieg akanga ari anorwisa-Nazi uye muNorway anodisa nyika uye akazvipira muna 1940 kurwisana nehutongi hweNazi. Munguva yechando ya1939-1940, Grieg akashanda muNorway Army muFinnmark pahusimbe hwekuchengetedza panguva yeRusso-Finnish Winter War. Muna 1940, mushure mekushandira panguva yeNorway Campaign kurwisa mauto eGerman, akatizira kuUnited Kingdom ari mungarava imwechete iyo yaitakura mhuri yeNorway Royal uye National Gold reserves. 