In a prelude to the Carnation Revolution, in the early morning of 16 March 1974, the Fifth Infantry Regiment (Regimento de Infantaria 5), based in Caldas da Rainha in what is now the School of Army Sergeants (Escola de Sargentos do Exército), attempted to stage a coup d'état against the country's authoritarian Estado Novo regime. Thirty officers and about 300 sergeants and enlisted men from the regiment left their quarters at 4:00 a.m., heading for Lisbon, where they planned to occupy the airport. On approaching the capital, the Caldas regiment found themselves alone, realizing that the other units supposed to participate in the coup had not joined the upheaval. The regiment turned back and reached their Caldas quarters at around 10:00 a.m., locking themselves in and awaiting a siege. The compound was surrounded by various forces, which penetrated the base at about 5:00 p.m. The revolters were arrested and sent to various military prisons, where they were held until the Carnation Revolution on 25 April 1974, 40 days later.