MEMORIES of a war between India and China are still vivid in the Tawang valley, a lovely, cloud-blown place high on the south-eastern flank of the Himalayas. They are nurtured first by the Indian army, humiliated in 1962 when the People’s Liberation Army swept into Tawang from next-door Tibet. India now has three army corps—about 100,000 troops—in its far north-eastern state of Arunachal Pradesh, which includes Tawang.

With another corps in reserve, and a few Sukhoi fighter planes deployed last year to neighbouring Assam, they are a meaty border force, unlike their hapless predecessors. In 1962 many Indian troops were sent shivering to the front in light cotton uniforms issued for Punjab’s fiery plains. In a weeklong assault the Chinese seized much of Arunachal, as well as a slab of Kashmir in the western Himalayas, and killed 3,000 Indian officers and men. Outside Tawang’s district headquarters a roadside memorial, built in the local Buddhist style, commemorates these dead. At a famous battle site, below the 14,000-foot pass that leads into Tawang, army convoys go slow, and salute their ghosts....