Complex sentence: Being a staunch Anti-Nazi, he emigrated to Britain and then later in 1940 to the United States, where he became professor at Columbia University and founded the Columbia Middle East Institute in 1948.
Split into simpler sentences: Being a staunch Anti-Nazi, he emigrated to Britain. In 1940 he migrated further to the United States, where he became professor at Columbia University and founded the Columbia Middle East Institute in 1948.