Complex sentence: He received his Ph.D. in 1938 with a dissertation on Matthew Arnold, which he later published, and in 1939 was promoted to assistant professor, becoming the first Jewish professor to receive tenure in the Department of English.
Split into simpler sentences: He received his Ph.D. in 1938 with a dissertation on Matthew Arnold, which he later published. In 1939 he received a promotion to assistant professor, the first Jewish professor to receive tenure in the Department of English.