In November 1947, the United Nations General Assembly endorsed a plan for the partition of Palestine, providing for the creation of an Arab State and a Jewish State, with Jerusalem to be placed under international status. The plan was not accepted by the Palestinian Arabs and Arab States. On 14 May 1948, the United Kingdom relinquished its mandate over Palestine and the State of Israel was proclaimed. On the following day, the Palestinian Arabs, assisted by Arab States, opened hostilities against Israel. Over the years, UNTSO military observers have remained in the Middle East to monitor ceasefires, supervise armistice agreements, prevent isolated incidents from escalating and assist other UN peacekeeping operations in the region. On 29 May 1948, the Security Council, in resolution 50 (1948), called for a cessation of hostilities in Palestine and decided that the truce should be supervised by the UN Mediator, with the assistance of a group of military observers. The first group of military observers, which has become known as the United Nations Truce Supervision Organization (UNTSO), arrived in the region in June 1948. In August 1949, the Security Council, by its resolution 73 (1949) assigned new functions to UNTSO in line with four Armistice Agreements between Israel and the four neighbouring Arab countries – Egypt, Jordan, Lebanon and the Syrian Arab Republic. UNTSO's activities thus were spread over the territory within five States in the region. Following the wars of 1956, 1967 and 1973, the functions of the UNTSO military observers have changed from time to time in light of changing circumstances, but they remained in the area, acting as go-betweens for the hostile parties and as the means by which isolated incidents could be contained and prevented from escalating into major conflicts. UNTSO personnel have also been available at short notice to form the nucleus of some other peacekeeping operations worldwide. The availability of UNTSO's military observers for almost immediate deployment after the Security Council had acted to create a new operation has been an enormous contributory factor to the success of those operations. (UNTSO website)
The first Chief of Staff of UNTSO was Major-General William E. Riley (1950), followed by Major-General E.L.M. Burns (1954), Major-General Carl C. von Horn (1960-1962), Lieutenant-General Odd Bull (1963-1969), Major-General Ensio Siilasvo (1970-1972), and Major-General Bengt Liljestrand (1974-1975). This post was changed to Assistant Secretary-General, Chief of Staff in 1980, with the following appointments: Major-General Emmanuel Alexander Erskine (1976-1977, 1981-1985), Major-General Erkki Raine Kaira (1980), Lieutenant-General William Callaghan (1986), Lieutenant-General Marin Vadset (1987-1989), Major-General Hand Christensen (1990-1991), and Krishna Narayan Singh Thapa (1992). In 1993, the post was vacant. The Officer-in-Charge in 1994 was Colonel Joseph Bujold, followed by Assistant Secretary-General, Officer-in-Charge Major-General Rufus Kupolati in 1995. Kupolati continued his post of Assistant Secretary-General, Chief of Staff from 1996-1997, followed by Major-General Timothy Ford (1998-1999), Major-General Franco-Ganguzza (2000-2001), Major-General Carl Dodd (2002-2003), and Brigadier General Clive William Lilley (2004-2006). He was succeeded by Head of Mission and Chief of Staff Major General Ian Gordon (2007-2009), Major General Robert Mood (2009-2010), and Major General Juha Kilpia (2011-present).