As Americans enjoyed their Independence Day fireworks last year, Lieutenant General Trey Obering, the Pentagon’s Missile Defence Agency chief, was watching the pyrotechnics display that Kim Jong-il was providing thousands of miles away in North Korea.

The air force general thought the launch by Pyongyang of its previously untested Taepodong-2, an intercontinental ballistic missile with the potential to reach the US, could even provide the first live use of America’s ballistic missile defence system.