launched a violent and repressive reaction in the period 1975–76. Though the FSLN was weakened, so was the regime. Collapse Direct U.S. military aid ended in November 1978 although the U.S. still attempted to pursue a policy of "Somocismo sin Somoza," effectively allowing the power structure of the National Guard to prevent a Sandinista victory while removing the increasingly unpopular Somoza from power. The Carter Administration even sent Somoza a congratulatory note from Carter after his disputed victory in the 1978 elections. After the assassination of opposition leader among the business elites Pedro Chamorro in January 1978, the Nicaraguan public reacted with a series of nationwide strikes and increasing political unrest against the regime. The National Guard was re-organized and expanded, growing to a force of more than 10,000 officers and enlisted men, with localized security companies dispersed throughout the country and modern specialized units such as mechanized and engineer battalions, a Presidential Guard, and a reinforced tactical battalion. The strengthened National Guard continued to tighten its grip but opposition only grew broader and fiercer. A humiliating hostage crisis ensued on 22 August 1978 when 25 Sandinista rebels disguised as National Guard soldiers led by "Comandante Cero" (Commander Zero), future Contra leader Edén Pastora, occupied the National Assembly Palace in Managua, took 2,000 hostages, and escaped to Panama with 50 released political prisoners. The seizure of the National Palace was the second major action launched by the Sandinistas. By March 1979, the Somoza regime faced an open civil war as well as being cut off from all aid by the United States, including blocking of an emergency shipment of weapons and ammunition coming from Israel. With ammunition, spare parts, fuel, and medical supplies running dangerously low, the increasingly hard-pressed National Guard could no longer sustain a prolonged fight against the rebels. Already plagued by shaky morale, and weakened by casualties and desertions after seven weeks of battle, GN units were gradually forced to fall back to Managua. At this point, on 17 July 1979 Somoza Debayle resigned from office and fled the country by plane to Miami, FL., followed by almost all of the senior military officers of the GN General Staff. Somoza's successor as head of state, interim President Francisco Urcuyo Maliaños opened negotiations for a cease-fire but at the same time tried to strengthen his political position by filling with younger colonels and lieutenant-colonels the depleted National Guard's