Dee ihe na-aga n'ihu maka paragraf a - N'afọ 1940, Marcantonio nyere aka guzobe American Peace Mobilization (APM), otu ndị ebumnuche ha bụ ime ka US ghara isonye na Agha Worldwa nke Abụọ (yabụ yiri ebumnuche nke aka nri America First Committee). Tupu a bịanyere aka na Molotov-Ribbentrop Pact (ọgbụgba ndụ ndị Nazi na Soviet na-adịghị emegide) na Moscow na 23 August 1939, ndị na-eduga na APM, ndị Comintern na-eduzi American League for Peace and Democracy, bụ ndị na-emegide ndị Nazi. Marcantonio jere ozi dịka osote onye isi oche nke APM. Ọ pụtara na akụkọ akụkọ na 1940 na-akatọ 'agha ndị ọchịchị aka ike', usoro nke Joseph Stalin na ndị na-akwado ya na Soviet Union ruo mgbe mwakpo nke Soviet Union site na Nazi Germany. Nkwekọrịta ahụ dịgidere ruo mgbe ndị Germany mebiri ya site n'imegide Soviet Union na June 22, 1941. Na 1942 Marcantonio rụsiri ọrụ ike iji gbasawanye njikọ aka ndị agha US n'ihu agha nke abụọ na Europe
megide mgbasawanye nke ndị Nazi. USSR nyere ndị Kọmunist n'ụwa nile iwu ịkwalite echiche ahụ iji nyere ya aka imeri Nazism. Marcantonio bụkwa osote onye isi oche nke International Workers Order, otu òtù ụmụnna na-erite uru nke na-abụghị nke ndị Kọmunist.