The Borrowdale Country Club, a once-elegant retreat in the northern suburbs of Harare, is a good place to measure the state of Zimbabwe’s beleaguered white population. Founded in the mid-1950s, when Zimbabwe was the British-administered colony known as Rhodesia, the club served as the sports and social center for two generations of ranchers, farmers, traders, administrators, and other members of the country’s once-coddled white minority. Above its polished mahogany bar, rows of plaques commemorate the winners of club tennis tournaments dating back fifty years; the wide veranda looks out over a lawn fringed by blooming jacarandas and frangipanis—and, beyond, a...