Complex sentence: Gromyko met and consulted with most of the senior officers of the United States government during his first days and succeeded Maxim Litvinov as ambassador to the United States in 1943.
Split into simpler sentences: Gromyko met and consulted with most of the senior officers of the United States government during his first days. Gromyko succeeded Maxim Litvinov as ambassador to the United States in 1943.