Fifty years ago, in 1973, the French author Jean Raspail released a then seemingly far-fetched novel titled “The Camp of the Saints,” which portrayed a massive influx of immigrants to France and Europe. Now, on the 50th anniversary of the book’s publication, the narrative feels eerily prescient as countries like Italy and Poland grapple with real immigration pressures. The powerhouse countries of Germany and France tend to set the agenda on the immigration issue, while countries like Poland and Italy find themselves responding to events rather than shaping them. Recent weeks have seen this topic heat up, especially in Italy,...