In the summer of 2020, China and India came near to war. The nuclear-armed adversaries both massed troops and equipment along their disputed border in eastern Ladakh. The two sides slugged it out with fists, stones and clubs, next to a fast-flowing Himalayan stream, resulting in dozens of deaths and injuries, many from hypothermia. The entire 4,000-kilometre Sino-Indian boundary is disputed. In 1962, the two countries fought a short and vicious war that went badly for India, and from which Nehru never recovered. The border, called the Line of Actual Control, is not marked on any map agreed upon by the two sides; it runs through the largely unpopulated and inhospitable high mountains of the Himalayas. From the 1990s, as Beijing and New Delhi sought to resolve their seemingly intractable border dispute, an elaborate system of agreements kept the situation akin to a kettle on a slow boil. But the kettle is now boiling over. The two rising Asian giants, both led by strongly nationalistic regimes, neither of which wishes to blink first, are seeking geopolitical and strategic advantage. This timely book explains what is happening on 'the roof of the world'; and why that matters for us all.