The fifth "John" who lost China

This is an old joke that people more educated about US-China relations than I am probably all know, but I got a kick out of it. In a review of John Paton Davies' autobiography, Roderick MacFarquhar writes,

In the 1950s, the late John King Fairbank, the dean of modern China studies at Harvard, used to tell us graduate students a joke about the allegation that a group of red-leaning foreign service officers and academics—the four Johns—had “lost” China: John Paton Davies, John Stewart Service, John Carter Vincent, and John King Fairbank himself. What the McCarthyites had forgotten, Fairbank said, was to finger the fifth “John”: John Kai-shek.