Foreign Policy reports on the nuclear arms race between China and India:

China and India have built up a $60-billion-per-year trading relationship, and for years they’ve insisted that they want to work more closely on a variety of fronts. Yet that expressed desire for collaboration co-exists uneasily with a long-running strategic rivalry. Parts of their mutual border remain in dispute. China has long supported Pakistan, India’s main enemy, while the Indians have often befriended competitors of the Chinese (be it Moscow or Washington). Lately Beijing has been cultivating relationships among countries in Southeast Asia and the Indian Ocean — including Bangladesh, Myanmar, and Sri Lanka — to protect the flow of commerce and access to supplies of natural resources. That has the Indians fearing encirclement.

Lately, though, another element is threatening to complicate the strategic calculus: the nuclear factor. In themselves, of course, nuclear weapons are nothing new to either country. China has been a nuclear power for decades, while India conducted its first nuclear test in 1974 (though most outsiders tend to think of 1998, when New Delhi conducted a series of underground explosions designed to establish its bona fides as a genuine nuclear power). Although both countries have sworn off first use, both have built up formidable deterrents designed to retaliate against any attackers.

So what’s new? A lot. Concurrent with their rising economic might, China and India have set about modernizing their militaries to lend extra muscle to their growing strategic ambitions — and given their complicated history, that can’t help but spark worries. “China has the most active and diverse ballistic missile development program in the world,” noted one U.S. report. “China’s ballistic missile force is expanding in both size and types of missiles.” China’s Dongfeng long-range missiles boast independently controlled multiple warheads, mobility, and solid fuel (meaning that they can be fired with little notice). That’s just one of many areas in which the Chinese have demonstrated their advanced technological capabilities. In January China shot down one of its own satellites with a missile — once again demonstrating, as it did with a previous test in 2007, that it’s well down the path toward a ballistic missile defense system.