He started working as a senior lecturer at the department of history.
In 1990-1991, he worked as the senior lecturer at the same school.
He has been a teacher and a senior lecturer in English.
In 1989, he joined Harvard as a senior lecturer on education.
He served as a senior lecturer at the time of his retirement after 22 years (1981 to 2002).
Charles was a senior lecturer in that department when he retired from academic life.
Holding the post for 26 years, he became senior lecturer in military history during his tenure.
He reached emeritus status in 1970 but continued as a senior lecturer for five more years.
He progressed to senior lecturer in 1965 and reader from 1970.
He became a senior lecturer at the university in 1981 and a professor in 1990.
