When Käthe Kollwitz, born in 1867, began creating portraits in 19th-century Prussia, the art world was dominated by men. Kollwitz was unfazed. Although she had trained as a painter, at 21 she switched to etching and sculpture, a truer calling. Later, she would use detailed lithographs to capture the crude reality of war. “I felt that I have no right to withdraw from the responsibility of being an advocate,” she wrote in her diary. “It is my duty to voice the sufferings of men.” In this large exhibition, the Städel celebrates her explosive power. —Elena Clavarino