China's testosterone problem.

Over the last decade, they cropped up in cities throughout China, tucked into raucous markets or along forgotten side streets, their interiors smelling of musty canvas and crammed with bounty for aspiring young soldiers: illicit weapons shops with names like ARMY GOODS STORE and GUNCOOL. For a few thousand yuan--a few hundred dollars--assault rifle-like air guns await in dirty back rooms, along with fatigues, bulletproof vests, kneepads, long underwear, camouflage t-shirts, rucksacks, bandoliers, helmets, helmet sleeves, walkie-talkies, and two-liter CamelBaks. Once outfitted, China's militiamen organize into clubs--Guangzhou Fight Men, Shanghai Band of Brothers, Tianjin Seals--and storm remote lots or abandoned warehouses, shooting at each other with pellets, to stage what they call "war games." The term belies the seriousness participants assign the activity: The more established clubs have dedicated battlegrounds whose surrounding trees are nailed with DANGER signs.

In gun-happy America, this hobby might not rise above the level of eccentricity; but, in China, where most weapons are illegal, it requires a special degree of passion. Beijing periodically cracks down, and clubs sometimes disappear overnight. In a round-up last year, Beijing cops seized 3,400 guns and knives used in war games. Still, the government can't seem to quash the urge among Chinese twentysomethings to unleash a few rounds. . . .

The macho violence spurting forth through outlets like war games is a growing trend in Chinese society--and China's one-child policy, in effect since 1979, is partly responsible. The country's three decades of iron-fisted population planning coincided with a binge in sex-selective abortions (Chinese traditionally favor sons, who carry on the family line) and a rise, even as the country developed, in female infant mortality. After almost 30 years of the policy, China now has the largest gender imbalance in the world, with 37 million more men than women and almost 20 percent more newborn boys than girls nationwide.

By the time these newborns reach puberty, war games may seem like a quaint relic. In the 2020s, Chinese Academy of Social Sciences researcher Zheng Zhenzhen, estimates in a People's Daily interview that 10 percent of Chinese men will be unable to find wives, which could have a huge impact on Chinese society. . . .

The one-child policy was instituted in an attempt to hamper the wild growth of the Chinese population. But, in the process of plugging one hole, the government may have left another open. The coming boom in restless young men promises to overhaul Chinese society in some potentially scary ways.