By then, Călinescu had masterminded a nation-wide clampdown against the Iron Guard, including Codreanu's physical liquidation. This resulted in a series of retaliatory attacks, peaking in September 1939, when a Guardist death squad managed to assassinate Călinescu. During November, Carol made one final attempt to establish a "national alliance" around the FRN, inviting Maniu to join in; the offer was dismissed. Mihalache held a seat in the Crown Council in early 1940, possibly because doing so toned down pressures on his friend Madgearu, whom Carol had placed under arrest. A political crisis began in Romania during June 1940, when the FRN government gave in to a Soviet ultimatum and withdrew its administration from Bessarabia. Maniu referred to this as a Soviet invasion, and believed that the Army should have resisted. In August 1940, after reassurances from both Nazi Germany and the Soviet Union, Regency Hungary asked Romania to negotiate territorial cessions in Transylvania. Maniu issued a public protest, demanding no reduction of territorial integrity.