Lebanon and Israel signed the General Armistice Agreement at Ras En Naqoura, ending active hostilities from the 1948 war and establishing an armistice line that would follow the international boundary (the Mandatory-era border), with supervision arrangements (including a Mixed Armistice Commission).
Israel’s March 1978 incursion into southern Lebanon (Operation Litani) prompted rapid UN Security Council action focused on restoring Lebanon’s territorial integrity and addressing the border area’s security dynamics.
The UN Security Council adopted Resolution 425, calling on Israel to withdraw from Lebanon and creating UNIFIL to confirm withdrawal and help restore international peace and security along the Israel–Lebanon area.
Israel began a major invasion of Lebanon on 6 June 1982 (often referred to as Operation Peace for Galilee), transforming the border dispute environment and leading to prolonged Israeli military presence in parts of Lebanon.
Lebanon and Israel signed the May 17 Agreement (a U.S.-mediated troop withdrawal and security framework). Although it aimed to formalize security arrangements linked to Israeli withdrawal, it soon became politically untenable in Lebanon.
Under intensifying internal conflict and external pressure, Lebanon announced the cancellation/abrogation of the May 17 Agreement, effectively ending that attempted framework for withdrawal-and-security arrangements.
Israel carried out a unilateral withdrawal from southern Lebanon over 24–25 May 2000, ending its long-running “security zone” posture and setting the stage for UN verification of the pullback line on the ground.
After technical work on the ground, UNIFIL formally transmitted the completed map of the withdrawal line to Lebanese and Israeli counterparts, creating what became known in UN usage as the “Blue Line” for confirming Israeli withdrawal (explicitly not a formal international boundary demarcation).
In report S/2000/590, the Secretary-General informed the Security Council that Israel had met the requirements for withdrawal from Lebanon in compliance with Resolution 425, based on the line identified by the United Nations (the Blue Line).
The Security Council endorsed the Secretary-General’s conclusion that Israel had withdrawn as of 16 June 2000, and noted that Israel and Lebanon had acknowledged the UN’s sole responsibility for identifying the withdrawal line and committed to respect it as identified.
The UN Security Council adopted Resolution 1559, reaffirming Lebanon’s sovereignty and calling for the withdrawal of remaining foreign forces and the disbanding/disarmament of Lebanese and non-Lebanese militias—issues directly affecting border security conditions south of the Litani and along the armistice/withdrawal lines.
The UN Security Council adopted Resolution 1680, strongly encouraging Syria to respond positively to Lebanon’s request to delineate their borders and establish diplomatic relations—reinforcing international emphasis on clear boundary definition in the wider Levant context alongside the still-provisional Israel–Lebanon land line (Blue Line).
To end the 2006 Israel–Hezbollah war, the UN Security Council adopted Resolution 1701, calling for a cessation of hostilities and addressing the security regime in southern Lebanon, including reference to Israel’s withdrawal behind the Blue Line and an expanded UNIFIL/Lebanese Armed Forces presence.
Israel–Lebanon boundary evolution and the 1949 armistice to the Blue Line (1949–2000+)
