In the literature of Chinese proverbs, patience is a much-prized and -honored virtue, but Chinese President Xi Jinping must surely be wondering if those ancient sages knew what they were talking about. Surely they never had to deal with North Korea and its bumptious new leader, Kim Jong Un.

A face-conscious China was badly embarrassed after North Korea ignored its pleas to cancel, or at least postpone, a recent nuclear test. And China is clearly worried about the U.S.'s announced "pivot" to the Pacific, focusing more military and diplomatic attention on the region.

Pyongyang regularly threatens to rain death, fire and destruction on South Korea, Japan and the United States, and China's response has been little more than an appeal for calm. But the three allies believe they must take these threats at least semi-seriously, and have beefed up their missile defenses, while Japan is rethinking its nuclear neutrality.

The U.S. sent two B-2s to the region, and the U.S. and South Korea have announced a tit-for-tat military response to North Korea's frequent military provocations. If North Korea shells a South Korean island, Seoul will do the same to the North; if North Korea sinks a South Korean ship, Seoul will return the favor. And the policy has U.S. backing.

And China? At an economic conference in China, Xi, with typical caution, not naming names, said, "No one should be allowed to throw a whole region or even the world into chaos for selfish games."

Everyone knew which nation he was talking about, but his circumspection was aimed at the Chinese People's Liberation Army, which sees value in keeping an impoverished North Korea, dependent on China for food and fuel, as a buffer state.

"Yet," according to The Wall Street Journal, "Chinese public opinion is turning against North Korea, and some academics are openly calling for China to turn its back on a socialist neighbor described in Chinese propaganda as being as 'close as lips and teeth.' "

Chinese patience and forbearance are admirable virtues, but not if they are used as an excuse to ignore reckless provocations. Kim Jong Un seems determined to find out how far he can go in taunting the West, and one day he will go too far.