India, Aug. 3 -- A reopened pass cannot undo six years of mistrust between India and China. But it can be the first plank of a bridge that can shorten the distance

On August 1, after a silence of more than six years, trade resumed across the frozen no-man's-land at Nathu La, the 14,140-foot Himalayan pass linking Sikkim to Tibet. Traders exchanged wool, silk, blankets and borax under the gaze of Indian and Chinese officials - a modest commercial event carrying outsized diplomatic weight. The numbers involved are trivial: the pass moved barely Rs 49 crore worth of goods in its last full year, a rounding error against bilateral trade nearing $150 billion. Yet few border crossings anywhere carry as much history per kilogram of yak wool.

Na...