to expel, enslave, or exterminate most Slavic people to provide "living space" for Germans, but 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. Between June 1941 and January 1942, the Nazis killed an estimated 2.8 million Red Army POWs, whom they viewed as "subhuman". In the years 1943–1945, around 120,000 Polish people, mostly women and children, became the victims of ethnicity-based massacres by the Ukrainian Insurgent Army, which was then operating in the territory of occupied Poland. In addition to Poles who represented the vast majority of the murdered people, the victims also included Jews, Armenians, Russians, and Ukrainians who were married to Poles or attempted to help them. During the intensification of ties with Nazi Germany in the 1930s, Ante Pavelić and the Ustaše and their idea of the Croatian nation became increasingly race-oriented. The Ustaše view of national and racial identity, as well as the theory of Serbs as an inferior race, was influenced by Croatian nationalists and intellectuals from the end of the 19th and the beginning of the 20th century. Serbs were primary targets of racial laws and murders in the puppet Independent State of Croatia (NDH); Jews and Roma were also targeted. The Ustaše introduced laws to strip Serbs of their citizenship, livelihoods, and possessions. During the genocide in the NDH, Serbs suffered among the highest casualty rates in Europe during the World War II, and the NDH was one of the most lethal regimes in the 20th century. German praise for America's institutional racism was continuous throughout the early 1930s, and Nazi lawyers were advocates of the use of American models. Race based U.S. citizenship laws and anti-miscegenation laws (no race mixing) directly inspired the Nazi's two principal Nuremberg racial laws—the Citizenship Law and the Blood Law. Hitler's 1925 memoir Mein Kampf was full of admiration for America's treatment of "coloreds". Nazi expansion eastward was accompanied with invocation of America's colonial expansion westward, with the accompanying actions toward the Native Americans. In 1928, Hitler praised Americans for having "gunned down the millions of Redskins to a few hundred thousand, and now keeps the modest remnant under observation in a cage." On