Terrorism in Sri Lanka has been a highly destructive phenomenon during the 20th and 21st centuries, especially so during the periods of the Sri Lankan Civil War (1983–2009) and the first (1971) and second JVP insurrections (1987–1989). A common definition of terrorism is the systematic or threatened use of violence to intimidate a population or government for political, religious, or ideological goals. Sri Lanka is a country that has experienced some of the worst known acts of modern terrorism, such as suicide bombings, massacres of civilians and assassination of political and social leaders. Terrorism has posed a significant threat to the society, economy and development of the country. The Prevention of Terrorism Act of 1978 is the legislation that provides the powers to law enforcement officers to deal with issues related to terrorism in Sri Lanka. It was first enacted as a temporary law in 1979 under the presidency of J. R. Jayewardene, and later made permanent in 1982. Terrorism found in Sri Lanka can be mainly categorized into three forms: ethno-nationalist terrorism, far-left terrorism and state terrorism. The Liberation Tigers of Tamil Eelam (LTTE) and Janatha Vimukthi Peramuna (JVP) are two of the most prominent and most deadly terrorist groups in Sri Lankan history. The LTTE, also known as Tamil Tigers, was a Sri Lankan Tamil militant group which waged an armed struggle against the Sri Lankan government and the Sinhalese ethnic majority for the purpose of establishing an independent Tamil ethnostate. This campaign led to the Sri Lankan Civil War, which ran from 1983 until 2009, when the LTTE was decisively defeated by the Sri Lanka Armed Forces. The Janatha Vimukthi Peramuna is a Marxist–Leninist communist party, which was involved in two armed uprisings against the ruling governments in 1971 (SLFP) and 1987–89 (UNP). After the two unsuccessful insurrections, the JVP entered democratic politics in 1994.