In their “The Central Intelligence Agency and Overhead Reconnaissance: The U-2 and OXCART Programs, 1954-1974”, Gregory W. Pedlow and Donald E. Welzenbach mentioned the U-2s operations in India.
[I quote from pages 231 to 233]
In October 1962, the People's Republic of China launched a series of massive surprise attacks against India's frontier forces in the western provinces of Jammu and Kashmir and in the North-East Frontier Agency (NEFA). The Chinese overran all Indian fortifications north of the Brahmaputra Valley before halting their operations.
The Indian Government appealed to the United States for military aid. In the negotiations that followed, it became apparent that Indian claims concerning the extent of the Chinese incursions could not be reliably evaluated. US Ambassador John Kenneth Galbraith, therefore, suggested to the Indian Government that US aerial reconnaissance of the disputed areas would provide both governments with a more accurate picture of the Communist Chinese incursions.
On 11 November 1962, Prime Minister Jawaharlal Nehru consented to the proposed operation and gave the United States permission to refuel the reconnaissance aircraft (U-2s) in Indian airspace.
In late November, Detachment G  to Ta Khli,  to carry out the overflights of the Sino-Indian border area. Since the U-2s were not authorized to overfly Burma, they had to reach the target area via the Bay of Bengal and eastern India and, therefore, required midair refueling.
Because of severe winter weather conditions, the first flight did not take place until 5 December. Poor weather and air turbulence hampered the mission, and only 40 percent of the target area could be photographed. A second mission on 10 December was more successful, but the U-2 experienced rough engine performance because of icing of the fuel lines.
Detachment G U-2s made four more overflights of the Sino-Indian border areas in January 1963, which led to a PRC protest to India. Photography from these missions was used in January and again in March 1963 to brief Prime Minister Nehru, who then informed the Indian Parliament about Communist Chinese troop movements along the border. Although Nehru did not reveal the source of his intelligence, a UPI wire story surmised that the information had been obtained by U-2s.
The United States had provided photographic coverage of the border area to India for two reasons. First of all, US policymakers wanted a clear picture of the area under dispute. In addition, the intelligence community wanted to establish a precedent for overflights from India, which could lead to obtaining a permanent staging base in India for electronic reconnaissance missions against the Soviet ABM [Anti-Ballistic Missile] site at Saryshagan and photographic missions against those portions of western China that were out of range of Detachment H.
In April 1963, Ambassador Galbraith and the Chief of Station at New Delhi made the first official request to India for a base. The following month, President Kennedy agreed to DCI [Director Central Intelligence] McCone's suggestion to raise the question of a U-2 base in India when he met with India's President Savepalli Radhakrishnan on 3 June. This meeting resulted in an Indian offer of an abandoned World War II base at Charbatia, south of Calcutta [near Cuttack in Odisha].
The Charbatia base was in poor condition and needed considerable renovation before it could be used for U-2 operations. Work on the base by the Indians took much longer than expected, so Detachment G continued to use Ta Khli when it staged four sorties over Tibet from 29 September to 10 November 1963. In addition to the coverage of the Sino-Indian border during this series of flights, the U-2s also photographed all of Thailand to produce a photomap of the border regions as a quid pro quo for the Thai Government. During one of these photomapping missions, a U-2 pilot conducted the longest mission ever recorded in this aircraft- 11 hours and 45 minutes.
At the end of this flight on 10 November 1963, the pilot was in such poor physical condition that project managers prohibited the scheduling of future missions longer than 10 hours.
Charbatia was still not ready in early 1964, so on 31 March 1964 Detachment G staged another mission from Ta Khli. The first mission out of Charbatia did not take place until 24 May 1964. Three days later Prime Minister Nehru died, and further operations were postponed.
The pilots and aircraft left Charbatia, but other equipment remained in place to save staging costs. In December 1964, when Sino-Indian tensions increased along the border, Detachment G returned to Charbatia and conducted three highly successful missions, satisfying all of COMOR's requirements for the Sino-Indian border region. By this time, however, Ta Khli had become the main base for Detachment G's Asian operations, and Charbatia served merely as a forward staging base. Charbatia was closed out in July 1967.
 Elsewhere, the U-2 report says that Detachment C could not have stayed in Nevada much longer. In June 1957, the entire facility had to be evacuated because the Atomic Energy Commission was about to conduct a series of nuclear tests whose fallout was expected to contaminate the Groom Lake facility. All remaining CIA personnel, materiel, and aircraft were transferred to Edwards Air Force Base in California, and became known as Detachment G.
 Takhli Royal Thai Air Force Base is today a Royal Thai Air Force facility, located in Central Thailand, approximately 144 miles northwest of Bangkok
What is surprising in this story is that the beginning of the collaboration between the CIA and the Indian Government for reconnaissance of the Himalayan borders, is given as November 11, 1962.
It is the day Nehru is supposed to have allowed the U-2s to 'refuel' during their reconnaissance flights.
To understand the context, it is necessary to look at The Foreign Relations of the United States (1961–1963 Volume XIX, South Asia), which publishes several telegrams from the Department of State to the US Embassy in India.
One of these cables is sent from Washington on November 20, 1962 (at 12:50 a.m. U.S. time) by the US Secretary of State Dean Rusk to the US Ambassador in India, John Kenneth Galbraith.
Marked ‘Eyes Only for Ambassador from Secretary’, the cable says of Nehru's request for assistance: “We have just forwarded to you second letter from Nehru today anticipated in your [cable] 1889. As we read this message it amounts to a request for an active and practically speaking unlimited military partnership between the United States and India to take on Chinese invasion India. This involves for us the most far-reaching political and strategic issues and we are not at all [emphasis mine] convinced that Indians are prepared to face the situation in the same terms. I recall that more than once in past two years I have expressed to various Indian representatives my concern that their policy would lead to a situation where they would call upon us for assistance when it is too late rather than give their and free world policy any opportunity for preventive effectiveness.”
This new development relates to the two panicky letters sent by the Indian Prime Minister on November 19, 1962, which were brought to the Indian public’s notice by the veteran journalist Inder Malhotra a few years ago.
Another telegram (also classified ‘Eyes Only for the Ambassador’) from Dean Rusk was sent the same day at 22:31 p.m. US time; it tells the US Ambassador: “Unless you think it inappropriate, please deliver the following message to Prime Minister Nehru as soon as feasible.”
The letter to Jawaharlal Nehru reads thus:
Dear Mr. Prime Minister:It is signed Dean Rusk, who told his Ambassador: “You might suggest to Nehru that even under changed circumstances the team would be useful as a tangible gesture of US support.”
I was on the point of responding to your two urgent letters when we received news of the Chinese statements on a cease-fire. I, of course, wish your assessment of whether it makes any change in your situation. I had planned to write you that we are ready to be as responsive as possible to your needs, in association with the United Kingdom and the Commonwealth. We remain prepared to do so.
We had already organized a small group of top U.S. officials [headed by Ambassador Averell Harriman, it included Paul Nitze, Carl Kaysen, Roger Hilsman, and General Paul D. Adams], who would arrive in New Delhi Friday [November 22], to help Ambassador Galbraith in concerting with your government how we can best help. It seems useful to go ahead with this effort as planned and we will do so unless you think it inadvisable.
In the earlier quoted telegram, the State Department had informed the US Ambassador: “Latest message from PriMin [Nehru] in effect proposes not only a military alliance between India and the United States but complete commitment by us to a fighting war. We recognized this might be immediate reaction of a Government in a desperate position but it is a proposal which cannot be reconciled with any further pretense of non-alignment. If this is what Nehru has in mind, he should be entirely clear about it before we even consider our own decision.”
The problem was that Washington (and Delhi as well) had little information about the Chinese intentions and even less on the dispositions of the PLA in Tibet. It was most urgent for both Washington and Delhi to get proper and reliable information; this probably justified the use of the U-2 surveillance planes.
This was what Ambassador Averell Harriman was sent to Delhi for: to ascertain Nehru’s long term intentions and India’s real needs.
Washington however warned: “There are strong reasons why the United States should not appear to be the point of the spear in assisting India in this situation. The most impelling of these is that our role might force Moscow to support Peiping [Beijing]. We shall be considering here whether there is anything we can constructively say to Moscow about China's reckless and provocative action because there is some reason to believe that Moscow is also very much worried about the dangerous possibility. I would emphasize, however, India must mobilize its own diplomatic and political resources, seek the broadest base of support throughout the world and, more particularly, enlist the active interest and participation of the Commonwealth.”
Already on November 19 (in the cable quoted earlier), Rusk had defined the possible help Washington could immediately provide to Delhi: “We are prepared to dispatch twelve or more C-130's at once to assist in any necessary movement of forces and equipment to Assam area or to Ladakh. This would be US operation with planes, crews support. Request your urgent advice whether Indians prepared to use this transport immediately. Also earliest estimates men and tonnage involved. Special airlift team being dispatched at once. This provides another opportunity for you to remind Indians about importance of moving troops from Pakistan border. Urgency of situation underlines anomaly of Indian reluctance in this respect.”
Part of the Harriman’s mission was also to make peace between India and Pakistan. This has been mentioned elsewhere on this blog.
Washington was keen to rope in the British in the operation.
As mentioned by The US Secretary of State in the same cable: “This as far as we can see to go on basis of facts now available here. However, supply actions urgently needed and assessed as valid need not be delayed despite lack of clear picture Indian capabilities. View possibility India now ready use tactical air, one airlift requirement may be bombs request of UK. London should raise this and ascertain availability and British air shipment capabilities.”
This is for the overt assistance; we have another source of the events, which mentions the covert support (minus the U-2’s reconnaissance flights).
Kenneth Conboy and James Morrison in their ‘The CIA'S Secret in Tibet’ (University Press of Kansas, 2002) recounts:
On 21 November, Harriman's entourage departed Andrews Air Force Base in Maryland. Although the Chinese declared a unilateral cease-fire while the group was en route, the situation was still tense when it reached New Delhi the following day. Without pause, Ambassador Galbraith ushered Harriman into the first of four meetings with Nehru. The end results of these discussions were plans for a major three-phase military aid package encompassing material support, help with domestic defense production, and possible assistance with air defenses.Convoy and Morrison, who are more interested by the covert aspect of the US-India collaboration (particularly the US support to the Tibetan guerilla), continue:
As a covert aside to Harriman's talks, the CIA representatives on the delegation held their own sessions with Indian intelligence czar [Intelligence Bureau Director B.N.] Mullik. This was a first, as Galbraith had previously taken great pains to downscale the agency's activities inside India to all but benign reporting functions. As recently as 5 November, he had objected to projected CIA plans due to the risk of exposure. But in a 13 November letter to Kennedy, the ambassador had a qualified change of heart, noting that [Defence Minister V.K. Krishna] Menon's departure was a turning point to begin working with the Indians on ‘sensitive matters’.Convoy and Morrison analyse: "Mullik was cautious as well. Although he was well connected to the Nehru family and had the prime minister's full approval to talk with the CIA, he knew that the Indian populace was fickle, and until recently, anti-Americanism had been a popular mantra. It was perhaps only a matter of time before the barometer would swing back and make open Indo-U.S. cooperation political suicide.”
Both the CIA and the Intelligence Bureau were quick to seize the opportunity. "I went into a huddle with Mullik and Des [FitzGerald, head of CIA’s Far East Division]," recalls Critchfield [James Critchfield of the CIA’s the Near East Division], "and we started coming up with all these schemes against the Chinese."
Most of their ideas centered around use of the Tibetans. "The Indians were interested in the Tibet program because of its intelligence collection value," said [India’s] station chief David Blee, who sat in on some of the meetings. "Mullik was particularly interested in paramilitary operations." There was good reason for this: following Menon's resignation, and [Dalai Lama's elder brother] Gyalo Thondup's stated preference, the Intelligence Bureau had been placed in charge of the 5,000 Tibetan guerrillas forming under Brigadier [Sujan Singh] Uban [first Inspector General of the Tibetan Special Frontier Force].
According to the American authors: “By the end of the Harriman mission, the CIA and Intelligence Bureau had arrived at a rough division of labor. The Indians, with CIA support from the Near East Division, would work together in developing Uban's 5,000-strong tactical guerrilla force. The CIA's Far East Division, meantime, would unilaterally create a strategic long-range resistance movement inside Tibet. The Mustang contingent would also remain under the CIA's unilateral control.”
But this is another story.
To come back to the U-2 operation in India, it is doubtful that a full-fledged use of the U-2s was permitted on November 11, though V.K. Krishna Menon, the arrogant Defence Minister and stumbling block for a closer collaboration between India and the US, had resigned on November 8.
It is also true that the CIA History of the U-2s mentions only the 'permission for refueling' given on November 11.
It is however certain, that the main thrust of the covert operations over the Himalayas was decided during Harriman's Mission to India, when the CIA's senior officials accompanying Kennedy's envoy met with their Indian counterpart, particularly B.N. Mullik.
Though not mentioned in the CIA's history, it would be interesting to probe the role of Biju Patnaik, the Oriya politician, who was instrumental in offering Charbatia as a base the U-2s' operations in the Himalayas and Tibet.
Early 1961, Patnaik became president of the Odisha's State Congress. Under his leadership, the Congress Party won 82 of 140 seats in the Assembly election and on 23 June 1961, he became the State Chief Minister (he remained in the post until 2 October 1963 when he resigned from the post under the Kamaraj Plan to revitalise the Congress party). Patnaik was then 45-year old.
He played an important, though not recognized as yet, in the covert operations against China.