The plot was planned by Antão Vaz de Almada, Miguel de Almeida and João Pinto Ribeiro. On 1 December 1640, they, together with several associates, known as the Forty Conspirators, took advantage of the fact that the Castilian troops were occupied on the other side of the peninsula and killed Secretary of State Miguel de Vasconcelos, imprisoning the king's cousin, the Duchess of Mantua, who had governed Portugal in his name. The moment was well chosen, as Philip's troops were at the time fighting the Thirty Years' War in addition to the revolt in Catalonia.