According to Ian Kershaw, Broszat made important contributions in four areas. From the late 1950s he worked on the history of Eastern Europe, especially Poland, and on Nazi concentration camps. This led to his exploration of the structure of the Nazi German state, which resulted in his book "Der Staat Hitlers" (1969), published in English as "The Hitler State" (1981). In the 1970s he became interested in "Alltagsgeschichte" and examined everyday life under the Nazis, developing the concept of ""Resistenz"" (immunity) and co-editing a six-volume work about Bavaria under National Socialism, "Bayern in der NS-Zeit" (1977–1983). Finally, in 1985, he began the debate about the "historicization" of Nazi Germany, arguing that it should be studied like any other period of history, without moralizing and with recognition of its complexity.