Robert Gates, US defence secretary, has for years been pressing China to be more transparent about the nature and scale of its arms build-up. He may now be regretting what he wished for. Mr Gates was welcomed to China this week with the first test flight of its military’s J-20 stealth fighter. That can only be seen as a deliberate snub and show of force to the US defence secretary, who had questioned China’s ability to build a credible strike fighter fleet much before 2020.

Two things stand out from the incident. First is Beijing’s growing assertiveness and willingness to thumb its nose at other countries. China hardened its position on a range of issues last year, for example offending Asian neighbours with its stance on territorial disputes in the South and East China seas. It has also taken a tougher line on Taiwan, breaking off military-to-military contacts with the US after Washington fulfilled a longstanding arms shipment to the island state. This week, General Liang Guanglie rebuffed Mr Gates’ request for a clear timetable on deeper defence talks, warning that a resumption of arms sales to Taiwan would lead to a further suspension of military contacts.

The second notable thing was that Hu Jintao, China’s president, was – according to US officials, at least – caught unawares by the timing of the stealth fighter test. That seems hard to believe. If he really did not know, it would suggest that the Chinese Communist party’s grip over the People’s Liberation Army is slipping. In any case, the PLA has become more willing to voice its opinion on foreign policy matters, a trend that appears to have contributed to China’s hardening posture abroad.