In 1986–87, a military standoff took place between India and China in the Sumdorong Chu Valley bordering the Tawang district, Arunachal Pradesh and Cona County, Tibet.

It was initiated by China moving a company of troops to Wangdung, a pasture to the south of Sumdorong Chu that India believed to be its territory.

[4] Under the orders of General Sundarji and codenamed Operation Falcon, the Indians undertook an airlift of troops and vehicles to Zemithang from 18 to 20 October 1986.

Taking up locations on multiple heights, including the Hathung La ridge, Indian troops were able to strategically occupy the high ground near Sumdorong Chu.

The first formal flag meeting to discuss “ the freezing of the situation” since 1962, was held on the fifth of August 1987 at Bum La in the aftermath of the Wangdung affair.

[10] The exercise involved 10 divisions of the Indian Army and several squadrons of the IAF and a redeployment of troops at several places in North East India.

[7] General Vishwa Nath Sharma has said that Operation Chequerboard was nothing but only a telecom and headquarters exercise and that Sundarji didn't move any brigades and there was nothing on the ground.

The agreement brought in an interesting concept of "mutual and equal security" where thinning of forces was envisaged, based on geographical and logistical considerations.

To strengthen the defence infrastructure India acquired the land near Lungroo La mountain pass in Lungroo Grazing Ground (LGG) 17 km away from Tawang town,[13] and under the India–China Border Roads (ICBRs) project started to build the strategic LGG-Damteng-Yangtse Road (LDY) to the Indian post near Chumi Gyatse Falls.