Were Fundamentalists Defeated in the 1930s and 1940s?

Nope.  At least not if you consider their amazing missions output in these decades.  This is my summary from Joel Carpenter’s marvelous Revive Us Again (Oxford, 1999), pages 28-29:

Modernism wrought devastating effects in the Northern Baptist Convention. It sent 845 staffers overseas in 1930; it sent 508 in 1940. From 1920 to 1936 the Northern Baptist budget for missions plummeted 45%. In 1936, no new missionaries were sent out from the Northern Baptists. In this same time, fundamentalists sent about 3000 missionaries to the field, and by the early 1950s had sent about 6000 of 19,000 total Protestant missionaries on the field. The China Inland Mission, for example, sent out about 700 new missionaries between 1930 and 1936. The Sudan Interior Mission had just 44 missionaries in 1920 but by 1945, it had 494 in active service. Between 1932 and 1942, at least 500 Moody Bible Institute alumni became missionaries, which brought the school’s total missionary production since its founding to about 2500 alumni.

If you want to understand the marginalization and building period of fundamentalism, get this book.

Carpenter’s text turns two ideas on their head: 1) that fundamentalists merely withdrew from culture (they were forcibly expelled as well) and 2) they fell into a state of senescence and defeat in the 1930s and ’40s.  Not true!  On the contrary, they began and strengthened many heroic and important works, as you can see above.