What is the story behind Pakistan Occupied Kashmir?

India claims POK to be it's part but Pakistan has the administration controls in that region. What is the real story behind POK? Who does it belong to; India or Pakistan? Is India right in claiming POK to be it's part? What is Line of Control between these two countries?

During British Rule, Jammu and Kashmir was an entity of British India that was not directly governed by the British, but rather by an Indian Ruler Maharaja Hari Singh the time of Partition, J&K was left with the options of joining India or Pakistan or remaining independent.

Hari Singh wanted his state to remain independent, for which he signed a stand-still agreement which stated that J&K need some time to think. Neither Pakistan nor India was ready to accept an independent Jammu and Kashmir. Few years later, there was a revolution by Muslims in the western part of Kashmir (Muzaffarabad).

J&K was connected to India through a district of the Punjab, but its population was 70 per cent Muslim and it shared a boundary with Pakistan. Hence, it was anticipated that the maharaja would accede to Pakistan when the British paramountcy ended on 15 August.

When he hesitated to do this, Pakistan launched an attack by which they meant to frighten its ruler into submission. Hari Singh tried to counter the invasion but failed. As a result,on 26 October Maharaja appealed to Lord Mountbatten (the last Viceroy Of British India and First Governor General of Independent India.), for assistance, Lord agreed on a condition that the ruler accede to India.

Maharaja Hari Singh's Letter to Mountbatten

The ruler signed the accession. Indian soldiers were immediately tranfered to Srinagar on October 27. India and Pakistan began their first war indo-pak war 1947 in less than three months of coming into being as independent states. Local tribal militias and the Pakistani forces moved to take Srinagar but on reaching Uri they encountered defensive forces. Indian and Pakistani armies entered the war subsequently. The fronts solidified gradually.

India approached the United Nations, asking it to solve the dispute. On 1 January 1949, a cease-fire line separating the Indian- and Pakistani-controlled parts of Kashmir was formally put into effect. In 1972, the then-current border between the Indian- and Pakistani-controlled parts of Kashmir was designated as the "Line Of Control"