The first UNIFIL troops arrived in Lebanon for peacekeeping mission along the Blue Line.

The Blue Line is a demarcation line between Lebanon and Israel and Lebanon and the Golan Heights published by the United Nations on 7 June 2000 for the purposes of determining whether Israel had fully withdrawn from Lebanon. It has been described as: "temporary" and "not a border, but a line of withdrawal.On 19 March 1978, the United Nations Security Council adopted Resolutions 425 and 426 calling for Israeli withdrawal from Lebanon following its recent invasion and to ensure that the government of Lebanon restores effective authority in the area to the border. The United Nations Security Council and NATO set up the United Nations Interim Force in Lebanon (UNIFIL) as a peacekeeping force to supervise the situation in Southern Lebanon.

By September 2018 Israel completed 11 kilometers of a concrete Israel-Lebanon barrier on the Israeli side of the demarcation line to protect Israeli communities from infiltration by Hezbollah militants. The length of the barrier is to be 130 kilometres (81 mi) and was expected to be complete by 2020. The project was expected to cost $450 million. Most of the barrier is a concrete wall topped by steel mesh, sensors and surveillance cameras. Steel fencing was to be used instead of concrete in especially rugged areas.

The United Nations Interim Force in Lebanon (Arabic: قوة الأمم المتحدة المؤقتة في لبنان, Hebrew: כוח האו"ם הזמני בלבנון), or UNIFIL (Arabic: يونيفيل, Hebrew: יוניפי״ל), is a UN peacekeeping mission established on 19 March 1978 by United Nations Security Council Resolutions 425 and 426, to confirm Israeli withdrawal from Lebanon which Israel had invaded five days prior, in order to ensure that the government of Lebanon would restore its effective authority in the area. The 1978 South Lebanon conflict came in the context of Palestinian insurgency in South Lebanon and the Lebanese Civil War.

The mandate had to be adjusted twice, due to the Israeli invasion of Lebanon in 1982 and after the Israeli withdrawal from Lebanon in 2000. Following the 2006 Lebanon War, the United Nations Security Council enhanced UNIFIL and decided that in addition to the original mandate, it would, among other things, monitor the cessation of hostilities; accompany and support the Lebanese Armed Forces as they deploy throughout the south of Lebanon; and extend its assistance to help ensure humanitarian access to civilian populations and the voluntary and safe return of displaced persons.

UNIFIL's mandate is renewed annually by the United Nations Security Council; it was most recently extended on 30 August 2021. It is composed of 10,000 peacekeepers from 46 nations, tasked with helping the Lebanese Army keep the south of the country protected. Its funding is approved on an annual basis by the General Assembly. It had a budget of $474 million for the period July 2018 to June 2019.