Oliver Cromwell was a Puritan and during the Interregnum, he imposed a very strict form of Christianity upon the country. Although a main cause of the English Civil War was oppression under Charles I, England during the Interregnum became oppressive in its own fashion. Cromwell granted religious freedom otherwise previously unknown in England, but other forms of expression were suddenly limited (for instance, theatre, which had thrived under the Stuart kings and Elizabeth I, was banned). Cromwell also made certain that his own personal vision of Christianity was enforced upon the masses. Many of Cromwell's actions were called "harsh, unwise, and tyrannical" by some commentators. 