The worldwide expansion of Christianity over the past century is a tide that has lifted virtually all denominations—with one apparent exception. A hundred years ago, any account of the Christian world would have recognized three great streams: the Roman Catholic, Protestant and Orthodox. After 1917, though, the Orthodox churches suffered a long period of disastrous persecution and disruption, preventing them from engaging in anything like the global missionary expansion that has built such powerful new foundations for other churches. Today, many Orthodox churches are based in European countries that are faced with an alarming demographic decline. At first sight, then, in terms of raw numbers, the Orthodox future looks grim.