Amid the growing popularity of the opposition, Marcos declared martial law on September 21, 1972, by virtue of Proclamation No. 1081 to stifle dissent. Marcos justified the declaration by citing the threat of Communist insurgency and the alleged ambush of defense secretary Juan Ponce Enrile. Ruling by decree, Marcos curtailed press freedom and other civil liberties, abolished Congress, closed down major media establishments, ordered the arrest of opposition leaders and militant activists, including his staunchest critics: senators Benigno Aquino, Jr., Jovito Salonga and Jose Diokno. Crime rates plunged dramatically after a curfew was implemented. Many protesters, students, and political opponents were forced to go into exile, and a number were killed.