The story of artist John Heartfield — born Helmut Franz Josef Herzfeld in Berlin in 1891 — begins like a German fairy tale. In 1899, his parents, ill and poverty-stricken, abandoned Helmut and his three siblings in a mountain cabin at Aigen, near Salzburg. The hungry children were discovered four days later by the mayor of the town and his wife, who took them in and fostered them. Meanwhile, their uncle, a lawyer, appeared with a trust from their wealthy grandfather’s estate to fund their educations. Helmut trained at several art schools in Germany, eventually arriving at the School of...