In China 30 years ago an audacious public protest in the capital’s central square pushed the country’s autocrats to the brink, and when the Soviet Union imploded, the ruling party’s most relentless critic became Russia’s president and dominant political figure. Ascendant America had no serious rival. In Europe, West welcomed East. Among the world’s most advanced countries, there seemed little left to fight over. The end to a century of conflict appeared to ensure democracy had carried the day.