The Oath of Engagement was the declaration of loyalty to the Commonwealth first proposed by Henry Ireton after the execution of King Charles I in 1649. Ireton wanted all members of the Council of State to sign a declaration expressing their approval of the King's trial and execution and of the abolition of the Monarchy and House of Lords. When several Councillors objected, a compromise was reached whereby they were required to declare loyalty to the republican Commonwealth, but did not have to declare their approval of its past actions.
In October 1649, the Engagement was extended to all Members of Parliament, all clergymen, all members of the armed forces and to all officials in the courts of law, in municipal government and at universities and schools.
Early in 1650, amid alarming rumours of Charles II's alliance with the Scots, Parliament voted to extend the Engagement to all adult males in England. In November, Parliament ordered the dismissal of clergymen who refused to take the Oath but in practice it proved impossible to enforce it across the general population, particularly as General Fairfax was among those who objected to it. The Oath of Engagement was finally repealed in January 1654 when Oliver Cromwell became Lord-Protector.