Why were Annemarie, Ellen, and Kirsti stopped by the soldiers?

One day, Annemarie, Ellen, and Annemarie’s five-year-old sister Kirsti walk home from school. Annemarie and Ellen decide to race, but two German soldiers stop them on the corner near their apartment building. The Germans question Annemarie about why she is running, but Kirsti manages to defuse the moment with her comically rude behavior.