why was it formed?
Before 1999 some East Timorese leaders,  proposed that a future East Timorese state would not have a military. The widespread violence and destruction that followed the independence referendum in 1999 and the need to provide employment to FALINTIL veterans led to a change in policy.
Timor Leste Defence Force
During the period before 1999 some East Timorese leaders, including the current President José Ramos-Horta, proposed that a future East Timorese state would not have a military. The widespread violence and destruction that followed the independence referendum in 1999 and the need to provide employment to FALINTIL veterans led to a change in policy. 
what is the timor leste defence force? A military body responsible for the defence of East Timor. when was it formed? February 2001 by whom? From the national liberation movement guerrilla army known as FALINTIL
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Timor Leste Defence Force [SEP] Pre-independence
The F-FDTL was formed from the national liberation movement guerrilla army known as FALINTIL (Portuguese acronym for "Forças Armadas de Libertação de Timor-Leste" or Armed Forces for the Liberation of East Timor). During the period before 1999 some East Timorese leaders, including the current President José Ramos-Horta, proposed that a future East Timorese state would not have a military. The widespread violence and destruction that followed the independence referendum in 1999 and the need to provide employment to FALINTIL veterans led to a change in policy. The inadequate number of police officers who were deployed to East Timor as part of the United Nations-led peacekeeping force contributed to high rates of crime.