The enemy of the enemy is my friend…at least until a better option comes along. This appears to be the guiding principle of geopolitics in the fault-line region where China and India rub together. It has tended to escape scrutiny from the West, due to the inaccessibility of the area and the labyrinth of language differences.

And, also, the sheer complexity and length of the conflicts involved, according to Bertil Lintner, a journalist who has not only spent decades watching the area but a lot of time traveling around it. His new book, Great Game East: India, China, and the Struggle for Asia’s Most Volatile Frontier, is no armchair study but the result of hands-on experience.

Lintner notes that on a number of occasions border disputes between China and India have led to armed conflict. But the Game is usually more about maneuvering for influence with the states, would-be states, and insurgency movements that form a chain from the Himalayas to the Bay of Bengal. Lintner supplies some helpful maps of the area, which illustrate the patchwork nature of the region.

The difficult geography and complicated colonial history gave rise to a plethora of small groups, tribes and clans, with distinct languages and customs. In some cases, states within the eastern section of the Indian federation were created to stitch the pieces together. There were some successes, but in others the outcome was a weak government plagued by insurgents—and the insurgent groups are themselves prone to factionalization and splits. Lintner counts more than a hundred ethnic militias operating within the newly created states. Manipur alone has 35, Assam has 34 and Tripura has 30. It quickly becomes a maze of acronyms and competing agendas.

At various times, China has covertly (sometimes not so covertly) supported insurgents with arms and money. The strategic goal is not always clear. It might be merely to keep the Indian government distracted, or it might be a form of payback for India’s support of the groups agitating over China’s occupation of Tibet, and its support of the Dalai Lama.

Cutting across this are the tensions between India, Pakistan, and Bangladesh, stemming from religious issues as much as from geopolitical goals. At the same time, China worries about the growing Islamic fundamentalism in its western provinces.

None of this shows much sign of changing, and the past decade has seen a new player on the scene. Burma (Lintner refuses to call it Myanmar, insisting that Burma is the historically correct name) is seen as both a buffer and a strategic counter, and China has spent years cultivating the relationship. But Burma is itself splintered along ethnic lines. In particular, a large chunk of territory on the Sino-Burmese border is controlled by the United Wa State Army. The UWSA evolved from a communist movement into an ethnic insurgency and then a viable government, and has been supported by China at every stage. When Lintner visited the Wa capital Panghsang, he found a booming region operating without regard to the central Burmese government. As it happens, most of the UWSA’s money comes from drug production, originally heroin but now methamphetamines as well. China is now reaping the whirlwind, facing a flood of drugs across the border.

China has hedged its bets by supporting the Burmese national government, and has invested heavily in infrastructure that would provide access to the Indian Ocean. But in the past few years the Burmese government has begun to lean away from China towards the U.S., as it moves haltingly towards democratic reform. Nevertheless, Burma has still been willing to cooperate with China on naval bases and listening posts on its western coast—that is, facing towards India.

In fact, Lintner believes that the focus of Indo-Sino conflict is moving towards the Indian Ocean. He speculates that China sees a greater presence in the Indian Ocean as a way to protect its oil imports and as a buttress for its territorial claims in the South China Sea. India is likewise flexing its maritime muscles, and the potential for clashes is growing.

Lintner is not optimistic about the future. He sees the “tournament of shadows” between two rising powers as likely to intensify, with the potential to draw in the U.S. and other countries. It is not a happy scenario but, says Lintner, that is how it is.

He lays all this out with careful authority, although there are times when the book is not easy to read. This is due more to the complexity of the subject than Lintner’s presentation. But make no mistake: this is an area that policymakers need to watch, and Great Game East is a good place to start.