As one can see on a modern map, the region is contested from three sides, at least. At the time an intervention from the Soviet Union or China would be the least desirable for both Pakistan and India. Support from any other outside force would have had to be indirect, as this region is of difficult geography far from the sea. This limits any potential aid from France, the British or Americans. The role of any other power at the time, represented by being in the UN, would have to be characterised at minimal. On the other hand, economic sanctions for non-compliance could hurt any war effort of either side quite quickly.
(Howard B. Schaffer: "The Limits of Influence. America’s Role in Kashmir", Brookings: Washington, 2009)
Physical 3D Map of Jammu and Kashmir
So the main contestants for the Indo-Pakistani War of 1947–1948
are now described as "Pakistan and India". This gives a wrong impression. The Pakistanis that wielded weapons were small and irregular troops at first. Free-lancers, infantry, guerilla. Equipped, financed and backed in many ways by the regular Pakistani army, but not part of it nor identical to the Pakistani army.
When the regular Indian army started their big offensive in early 1948 that provoked the regular Pakistani army to enter the theatre. During Operation Easy tanks were employed for the first time.
After about six months of fighting, Indias military superiority began to tell. This led Pakistan to commit three brigades of regular troops in April 1948. Pakistan was able to occupy the areas they call AJK partly because it had excellent logistical access from north Punjab and NWFP, and partly because the people theremostly Punjabi-dialect speakerswere more under the influence of the Muslim Conference than Abdullahs NC. Similarly, Pakistan could occupy the Northern Areas (the Gilgit Agency and most of Baltistan) because the area had few roads and they could be accessed better from the Pakistani side. But what Pakistan wanted mostthe Kashmir Valleyeluded it. Indias superior military power and Sheikh Abdullahs grip on the population proved too much.
Peace efforts paralleled the fighting. IndiaPakistan meetings were held in Delhi and Lahore from 30 October to 8 December 1947 under the auspices of the Joint Defence Council of the two dominions, but no agreement could be reached. On 1 January 1948, India lodged a formal complaint with the UN under Article 35 of the UN Charter. The UN, then in just the third year of its life, was firmly under the control of the US and the UK. Of the other Security Council permanent members, Kuomintang China and pre-de Gaulle France were closely allied with them and the Soviet Union had yet to become a major international player. After an initial resolution seeking restraint by both sides, the United Nations Security Council (UNSC) passed a substantive resolution three days later, on 20 January 1948, setting up a three-member United Nations Commission for India and Pakistan (UNCIP). Both sides accepted these resolutions.
To India's chagrin the trend of opinion in the UN, beginning early February, began to veer towards Pakistans side. The geo-political interests of the US and the UK in West Asia as well as the framing of the issue in Hindu-Muslim terms played their part in this. The UNSC passed its first resolution on the settlement of the Kashmir problem on 21 April. The resolution called for the withdrawal of all Pakistani forces, a minimum presence by India, the appointment of a plebiscite administrator, and finally, plebiscite. Both sides rejected the resolution. On 13 August 1948 the UNCIP adopted its first resolution. Besides calling for a ceasefire, it asked Pakistan to withdraw all its troops and nationals from J&K and India to withdraw the bulk of its forces. It asked both countries to reaffirm their agreement to decide the disposition of the state in accordance with the will of the people. India accepted this resolution in broad terms while Pakistan, in effect, rejected it. Pakistan logically acknowledged the fact that with Abdullahs strong hold over the majority of the states Muslims and the presence of Indian troops in the state, a plebiscite verdict would go against it. In December, both sides agreed to accept the ceasefire part of the UNCIP resolution, and an agreement was signed on 1 January 1949. On 27 July 1949, military representatives of India and Pakistan signed the Karachi Agreement demarcating the ceasefire line up to Point NJ 9842 near the Siachen glacier. Troop withdrawals behind the ceasefire line were completed by 31 October.
Koithara, p 34–36.
This resolution urged the government of Pakistan “to use its best endeavors” to “secure the withdrawal from the State of Jammu and Kashmir of tribesmen and Pakistani nationals not normally resident therein who have entered the State for the purpose of fighting.” Once UNCIP was satisfied that such a withdrawal was taking place, the government of India was urged to “put into operation in consultation with the Commission a plan for withdrawing their own forces from Jammu and Kashmir and reducing them progressively to the minimum strength required for the support of civil power in the maintenance of law and order.” Once this was achieved, the resolution said that “the Government of India should undertake that there will be established in Jammu and Kashmir a Plebiscite Administration to hold a plebiscite as soon as possible on the question of the accession of the State to India or Pakistan.”
Bose 2005, p 39.
And Kashmir was not the only region with upheaval and violence during the partition Independence, population transfer, and violence. Such a situation can easily spin out of control. That is further out of control than it did already.
That means we have a combination of:
tactical restraint to avoid an escalation into a war along the whole border, real war between India and Pakistan, instead of a localised conflict (WP: Casualties and losses India: 1,104 killed, 3,154 wounded; Pakistan: 6,000 killed, ~14,000 wounded)
strategic considerations from both sides, heavily influenced by international opinion and even more so by outside interests. Both sides being pressured but trying to keep their options for a better time.
(Sumantra Bose: "Contested Lands: Israel-Palestine, Kashmir, Bosnia, Cyprus, and Sri Lanka", Harvard University Press, 2007.)
(Praveen Swami: "India, Pakistan and the Secret Jihad: The Covert War in Kashmir, 1947-2004 (Asian Security Studies)", Routledge: London, New York, 2006.)
(Sumantra Bose: "Kashmir: Roots of Conflict, Paths to Peace", Harvard University Press, 2005)
(Eric Margolis: "War at the Top of the World : The Struggle for Afghanistan, Kashmir and Tibet", Routledge: New York, 2001.)
(Verghese Koithara: "Crafting peace in Kashmir: Through a Realist Lens", Sage: New Delhi, Thousand Oaks, 2004.)