Biggerstaff served the U.S. State Department as a China expert during World War II, becoming the Chinese language secretary at the U.S. embassy in Chongqing. In 1946, he assisted ultimately unsuccessful U.S. efforts to construct a peace plan to avert the Chinese civil war.
In the 1950s, in part because of his status as an expert on China, he was branded a communist sympathizer by Senator Joseph McCarthy, an accusation which took years to fight off - a feat at which he was ultimately successful.