Looking at the green line

A buffer zone in Cyprus was first established in 1964, when Major-General Peter Young was the commander of the British peace force set up in the wake of the inter-communal violence of the early 1960s. After stationing his troops in different areas of Nicosia, the general drew a cease-fire line on a map with a green chinagraph pencil, which was to become known as the "Green Line". It later transpired that the map General Young was using had been borrowed from Major Bill Garbutt of the 14th/20th King's Hussars, whose clerk, Lance Corporal Arnie Greenwood, had marked the cease fire line on the map with the only coloured writing instrument that he had, which happened to be green.
 
The Green Line became impassable following the July 1974 Turkish invasion of Cyprus during which Turkey captured approximately 37% of Cypriot territory in response to a short-lived Greek Cypriot coup. A "security zone" was established after the Tripartite Conference of Geneva in July 1974. Pursuant to United Nations Security Council Resolution 353 (1974), the foreign ministers of Greece, Turkey, and the United Kingdom convened in Geneva, Switzerland, on 25 July 1974. According to UNFICYP, the text of the joint declaration transmitted to the Secretary-General of the United Nations was as follows: 
A security zone of a size to be determined by representatives of Greece, Turkey, and the United Kingdom, in consultation with UNFICYP, was to be established at the limit of the areas occupied by the Turkish armed forces. This zone was to be entered by no forces other than those of UNFICYP, which was to supervise the prohibition of entry. Pending the determination of the size and character of the security zone, the existing area between the two forces was not to be breached by any forces.
— Tripartite Conference & Geneva Declaration, 
 
The UN Security Council then adopted the above declaration with Resolution 355. When the coup dissolved, the Turkish Armed Forces advanced to capture approximately 37% of the island and met the "Green Line". The meandering Buffer Zone marks the southernmost points that the Turkish troops occupied during the Turkish Invasion of Cyprus in August 1974, running between the cease fire lines of the Cypriot National Guard and Turkish army that de facto divides Cyprus into two, cutting through the capital of Nicosia. With the self-proclamation of the internationally unrecognized "Turkish Republic of Northern Cyprus", the Buffer Zone became its de facto southern border.
Traffic across the buffer zone was very limited until 2003, when the number of crossings and the rules governing them were relaxed.
The Cyprus dispute, also known as the Cyprus conflict, Cyprus issue or Cyprus problem, is the ongoing issue of Turkish military invasion and occupation of the northern third of the island since 1974. Although the Republic of Cyprus is recognized as the sole legitimate state—sovereign over allthe island—the north is under the de facto administration of the self-declared Turkish Republic of Northern Cyprus, which is guarded by Turkish Armed  forces. Only Turkey recognizes the Turkish Republic of Northern Cyprus, while there is broad recognition that the ongoing military presence constitutes occupation of territories that belong to the Republic of Cyprus. According to the European Court of Human Rights, the Turkish Republic of Northern Cyprus should be considered a puppet state under effective Turkish control.
 
Initially, with the occupation of the island by the British Empire from the Ottoman Empire in 1878 and subsequent annexation in 1925, the "Cyprus dispute" was identified as the conflict between the people of Cyprus and the British Crown regarding the Cypriots' demand for self-determination. The British administration shifted the dispute from a colonial dispute to an ethnic dispute between the Turkish and Greek islanders.The international complications of the dispute stretch beyond the boundaries of the island of Cyprus itself and involve the guarantor powers under the Zürich and London Agreement(Turkey, Greece, and the United Kingdom), the United Nations and the European Union, along with (unofficially) the United States.
 
The 1974 Cypriot coup d'état ordered and executed by the Greek junta was followed five days later by Turkey's invasion-intervention leading to the occupation of the northern part of the internationally recognized Republic of Cyprus. In 1983, the Turkish Cypriot community unilaterally declared independence, forming the Turkish Republic of Northern Cyprus, a sovereign entity that lacks international recognition with the exception of Turkey,with which Northern Cyprus enjoys full diplomatic relations, in violation of Resolution 550, adopted on 11 May 1984 by the United Nations Security Council. 
As a result of the two communities and the guarantor countries committing themselves to finding a peaceful solution to the dispute, the United Nations maintain a buffer zone (known as the "Green Line") to avoid any further intercommunal tensions and hostilities. This zone separates the southern areas of the Republic of Cyprus (predominately inhabited by Greek Cypriots), from the northern areas (where Turkish Cypriots and Turkish settlers are a majority). Recent years have seen warming of relations between Greek and Turkish Cypriots, with officially renewed reunification talks beginning in early 2014, though the talks have continuously stalled and resumed multiple times since they began.