Jeremy Page

A year after the collapse of the Soviet Union, a cash-strapped Kremlin began selling China a chunk of its vast military arsenal, including the pride of the Russian air force, the Sukhoi-27 fighter jet.

For the next 15 years, Russia was China's biggest arms supplier, providing $20 billion to $30 billion of fighters, destroyers, submarines, tanks and missiles. It even sold Beijing a license to make the Su-27 fighter jet—with imported Russian parts.

Today, Russia's military bonanza is over, and China's is just beginning.

After decades of importing and reverse-engineering Russian arms, China has reached a tipping point: It now can produce many of its own advanced weapons—including high-tech fighter jets like the Su-27—and is on the verge of building an aircraft carrier.

Not only have Chinese engineers cloned the prized Su-27's avionics and radar but they are fitting it with the last piece in the technological puzzle, a Chinese jet engine.

In the past two years, Beijing hasn't placed a major order from Moscow.

Now, China is starting to export much of this weaponry, undercutting Russia in the developing world, and potentially altering the military balance in several of the world's flash points.

This epochal turnaround was palpable in the Russian pavilion at November's Airshow China in the southern city of Zhuhai. Russia used to be the star of this show, wowing visitors with its "Russian Knights" aerobatic team, showing off fighters, helicopters and cargo planes, and sealing multibillion dollar deals on the sidelines.

This year, it didn't bring a single real aircraft—only a handful of plastic miniatures, tended by a few dozen bored sales staff.

China, by contrast, laid on its biggest commercial display of military technology—almost all based on Russian know-how.