 Slavic nations such as the Slovaks, Bulgarians, and Croats, who collaborated with Nazi Germany were perceived as ethnically superior to other Slavs, mostly due to pseudoscientific theories about these nations having a considerable admixture of Germanic blood.In the secret plan Generalplan Ost ("Master Plan East") the Nazis resolved to expel, enslave, or exterminate most Slavic people to provide "living space" for Germans, however Nazi policy towards Slavs changed during World War II due to manpower shortages which necessitated limited Slavic participation in the Waffen-SS.Significant war crimes were committed against Slavs, particularly Poles, and Soviet POWs had a far higher mortality rate than their American and British counterparts due to deliberate neglect and mistreatment.