The Siachen Glacier

The Sumdorong Chu Incident


The Sino-Indian border has been a long and vexed issue and its role in the 1962 conflict needs no elaboration. Barring an armed clash at Nathu La in eastern Sikkim in 1967, the border between India and China (Tibet) – and specifically the ill-defined Line of Actual Control (LAC) in Ladakh/Aksai Chin and Arunachal Pradesh - had remained free of any major incidents through the '70s and the early '80s. While relations between the countries remained frosty for the most part, official statements from Beijing and New Delhi professed a desire to solve the border tangle peacefully through mutual consultations. Beginning in 1981, officials from both countries held yearly talks on the border issue and these talks continued till 1989 [1]. The 7th round of border talks held in July 1986 was overshadowed by reports in the Indian media of Chinese incursions into the Sumdorong Chu valley in Arunachal Pradesh. This was followed by reports of large-scale troop movements on both sides of the border in early 1987, and grave concerns about a possible military clash over the border. While this incident raised the temperature in Delhi and Beijing for a while, it soon faded from the headlines, overtaken by other events in both sides of the border - Operation Brasstacks, Rajiv Gandhi's visit to China in 1988, and the Tianamen Square incident in 1989 among others.

This article is an attempt to piece together the events that occurred, beginning in the summer of 1986 at the Sumdorong Chu valley. A description of the initial incident is followed by the subsequent escalation in tension in early 1987 and the diplomatic steps taken to cool those tensions. In the concluding section, some speculations concerning the motives behind the actions of the two countries are examined.

The Incident: June - October 1986

Sumdorong Chu (S-C) - referred to as Sangduoluo He in the Chinese media - is a rivulet flowing north-south in the Thag La triangle, bounded by Bhutan in the west and the Thag La ridge to the north. On June 26, 1986, the Government of India (GoI) lodged a formal protest with Beijing against intrusions in this region by Chinese troops, that had occurred beginning on June 16. Beijing denied any such intrusions and maintained that its troops were in a location north of the McMahon Line (ML), while the official Indian stance was that the Chinese troops had intruded south of the ML. (The actual region of the incursion has been described as the Thandrong pasture on the banks of the S-C, and also as the Wangdung region - which comes under the Zimithang circle of Tawang district [2]). This region has been located to the north of the ML by outside sources [3,4], as also by independent Indian observers [5,6].

This region falls along a traditional route from Lhasa to Tawang - and from there to the Brahmaputra valley - and the nearby Thag La ridge had witnessed serious clashes in the '62 conflict. The area had been considered a neutral area by both sides since 1962/63 [5,6] and had not been monitored by India between 1977 and 1980 [4]. However with the improvement of logistics on the Indian side, the Indian Army sought to reinforce and strengthen forward areas in Arunachal Pradesh in the early '80s. Patrols resumed in 1981 and by the summer of 1984 India had established an observation post on the bank of S-C [5,6] – which apparently afforded a view of Chinese positions on the other side of Thag La [3]. This post was manned by personnel of the Special Security Bureau (SSB) through the summer and vacated in the winter. In June of 1986, when a patrol from the 12th Assam Regiment returned to the area, it found a sizable number of Chinese already present, engaged in constructing permanent structures [2,8].

Initial reports put the number of Chinese at 40 - some of them armed and in uniform - who were soon reinforced to a total strength of about 200 men. Statements by Indian ministers in the Parliament described the intrusion as being between 1-2 km deep as the crow flies, supplied by mules along a 7 km trail [2]. By August the Chinese had constructed a helipad and began supplying their troops by air. Regarding the Chinese presence as a fait accompli and to prevent further 'nibbling', the Indian Army began aggressive patrolling across Arunachal Pradesh at other vulnerable areas. In September ’86 – while under pressure from both the public and opposition MPs to adopt a strong posture - the GoI sought a way out of the crisis by suggesting that if the Chinese withdrew in the coming winter, India would not re-occupy the area in the following summer. This offer was rejected by China whose troops were by now prepared to stay through the winter. By September-October, an entire Indian Army brigade of the 5th Mtn. Division was airlifted to Zimithang, a helipad very close to the S-C valley. Referred to as Operation Falcon [7,9], this involved the occupation of ridges overlooking the S-C valley, including Langrola and the Hathung La ridge across the Namka Chu rivulet. (These ridges are to the south of Thag La.)

Escalation: October '86 - May '87

In October, the Chinese leader Deng Xiaoping warned N.Delhi that if it continued nibbling across the border, China would have to "teach India a lesson" [10]. This threat – identical to that made to Vietnam in 1979 - was conveyed by the US Defense Secretary during a stopover in N.Delhi from Beijing. The rise in tensions was not helped, when in December 1986, Arunachal Pradesh was made a full state of the Indian Union. This drew a chorus of protests from across the border and Indian reactions that any change in Arunachal Pradesh’s administrative status was an internal matter. The spring and summer of 1987 saw media reports of heavy troop movements on both sides of the border and the very real possibility of a serious military clash [11,12,13]. Deng Xiaoping's earlier warning was conveyed again on March - this time by the US Secretary of State. By spring '87, Indian and Chinese camps were right next to each other in the S-C valley [3,10].

China – which has always had a large military presence in Tibet since its occupation – was said to have moved in 20,000 troops from the "53rd Army Corps in Chengdu and the 13th Army in Lanzhou" [23] by early 1987 along with heavy artillery and helicopters. By early April, it had moved 8 divisions to eastern Tibet as a prelude to possible belligerent action [6].

Troop reinforcements on the Indian side – which had begun with Operation Falcon in late 1986 – continued through early ’87 under a massive air-land exercise. Titled Exercise Chequerboard, it involved 10 divisions of the Army and several squadrons of the IAF and redeployment of troops at several places in the North-East. The Indian Army moved 3 divisions to positions around Wangdung [14], where they were supplied and maintained solely by air. These troop reinforcements were over and above the 50,000 troops already present across Arunachal Pradesh [11].

Denouement: May '87 - present

Rising tensions were lowered after a visit to China by the Indian External Affairs Minister in May 1987, where both sides reaffirmed their desire to continue talks on the border issue and to cool things down on the border. In August '87, Indian and Chinese troops moved their respective posts slightly apart in the S-C valley, after a meeting of the field commanders. During the 8th round of border talks on November '87, it was decided to upgrade the talks from the bureaucratic to the political level. Following Rajiv Gandhi's visit to China in 1988, a Joint Working Group (JWG) was set up to discuss, among other things, the alignment of the LAC [15]. In 1993, an agreement was inked between the foreign ministers of the two countries on the reduction of troops along the LAC. It was decided to pull back from respective forward check posts in the S-C valley from a situation of "close confrontation" and in 1994, the Indian MEA described the situation as one of "close proximity" where the respective posts were 50-100 yards apart [16]. Following the JWG meeting on April 1995, the two sides agreed to a simultaneous withdrawal of their troops from the four border posts - two Indian and two Chinese - in the S-C valley [3,15,17]. As of June 1999, the valley was unoccupied by either army, and their respective posts in the area were close to a kilometre apart [18].


The initial incident at S-C valley, viz. the establishment of a SSB post in the summer of 1985, can be considered to be a consequence of the uncertain and disputed nature of the LAC. The Indian side has been criticized by some [5] for being the first to intrude in a neutral area, and the subsequent events characterized as a Chinese reaction to India's 'forward policy' in the early '80s.

On the other hand, there is no unanimity as to the reason an isolated incident on the border should have led to such an increase in tension in early 1987. Prevailing international and domestic developments have been suggested as possible explanations. The troop reinforcements on the Indian side in the later months - during Operation Falcon, leading on to Exercise Chequerboard - have been thought by some to be an Indian reaction to growing Sino-Soviet rapprochement in 1986 [1,11]. The Indian reactions were apparently to test the extent of normalization in relations between China and the USSR and its effect on the Indo-Soviet relations. Reiterating his analysis of the 1962 conflict, Maxwell holds India solely responsible for the escalation [12], claiming the incident to be Rajiv Gandhi's method of provoking a confrontation with China in order to unite the nation and facilitate the imposition of an internal emergency. Regardless of the plausibility of some the explanations offered, many observers are agreed on the effect of the robust military moves on the Indian side. It is believed that the Indian Army used the events through 1986/87 both as an effective palliative for the bitter events of 1962, and to demonstrate the difference in the ground situation since that time, to the Chinese military [6,19,20,21].

On Chinese motivations behind the escalation, the consensus view seems to be that it was part of a strategy of indicating that the border issue in the Eastern sector was far from settled. While the early border talks had focussed mainly on the Aksai Chin region and not on the Eastern sector, the mid-'80s saw a change in Chinese attitude. The Chinese strategy changed to linking the border issues in the Eastern and Western sector, and demanding matching concessions in the Eastern sector for any Chinese withdrawals in Aksai Chin/Ladakh, in contrast to the Indian position that the two sectors be considered separately. In this view, a Chinese reluctance to react to a strong Indian military presence near or over the ML would weaken their negotiating position.

While an exchange of maps of the LAC would be an essential step towards the avoidance of such incidents, and eventually to a resolution of the boundary dispute, there has been a marked Chinese reluctance to comply with this, even after several years into the multi-level border talks [22]. There have been some reports following President Narayanan’s recent visit to China, of the increasing likelihood of such an exchange, particularly in the "middle sector" (Uttar Pradesh and Himachal Pradesh) [24,25]. It remains to be seen if such an event comes to pass.


  1. "Sino-Indian Border Talks 1981-1989: A View from New Delhi", Sumit Ganguly, Asian Survey, Vol.29, n.12, December 1989.
  2. China Report , compilation of news reports in Vol. 23, Nos. 1 & 3, 1987, published by The Centre for the Study of Developing Societies, N.Delhi.
  3. "Sino-Indian Border Dispute Reconsidered", Neville Maxwell, Economic & Political Weekly, Vol. 34, No. 15, April 10-16, 1999.
  1. The Economist, May 23, 1987. The S-C valley "seemed to lie to the north of the McMahon line; but is south of the highest ridge in the area, and the McMahon line is meant to follow the highest points". The highest ridge in the area is the Thag La (claimed by India to be on the border), which is actually to the north of the McMahon Line as drawn on a map.
  2. Gopal Ji Malaviya in "Indian and Chinese Foreign Policies in Perspective", edited by Surjit Man Singh, 1998, Radiant Publishers, N.Delhi.
  3. The Militarization of Mother India, Ravi Rikhye, 1990, Chanakya Pub. N.Delhi.
  4. "George in the China Shop", India Today, May 18, 1998 -
  5. "Midstream: George and the Dragon", Rakshat Puri, The Hindustan Times, April 22, 1998
  6. "Warrior as Scholar", India Today, February 22, 1999 -
  7. "China and India: Moving beyond Confrontation", Surjit Mansingh and Steven Levine, Problems of Communism, Vol. 38, no. 2-3, Mar-June 1989.
  8. "Eye-witness in Tibet", Far Eastern Economic Review, June 4, 1987.
  9. "Towards India’s Second China War?", Neville Maxwell, South, May 1987.
  10. "The Dragon’s Teeth", India Today, August 15, 1987.
  11. "Disputed Legacy", India Today, May 15, 1988.
  12. "Sino-Indian CBMs: Problems and Prospects",Swaran Singh, Strategic Analysis, July 1997, Vol.20, n.4
  13. "Parliament and Foreign Policy - Reflections on India-China Relations", Naheed Murtaza, 1998, Cadplan Pub., N.Delhi.
  14. Reuters report on August 21, 1995 -
  15. "A Border which is Quiet and Tension Free", Barun Das Gupta, The Hindu, June 7, 1999
  16. "Getting Tough With China: Negotiating Equitable, Not "Equal" Security", Bharat Karnad, Strategic Analysis, January 1998, Vol. 21, n.10
  17. "China's Long March to World Power Status: Strategic Challenge for India", Gurmeet Kanwal, Strategic Analysis, February 1999, Vol. 22, n.11
  18. "The China Syndrome", The Hindustan Times, June 6, 1999
  19. "Time to Draw the Line", Brahma Chellaney, The Hindustan Times, November 17, 1999
  20. Quoted portion taken from [10]. However, most reports on the PLA assign the 13th Group Army to the Chengdu Military Region, and there is no mention of a 53rd Group Army (or Corps) in the PLA.
  21. "Sino-Indian JWG to meet often", The Hindu, July 23, 2000
  22. "Sino-Indian Border Talks Next Week", The Hindu, November 11, 2000
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