A decade ago, under the late President Kim Dae-Jung, South Korea tried to pursue the "Sunshine Policy" – their own form of détente.

The president visited North Korea in 2001, and a series of economic and political events occurred trying to encourage deeper links. Among these were the family visits, reuniting those tragically separated after the Korean War in 1950-53, when the 38th parallel became the heavily fortified demarcation line.

In the last decade, things have turned out far tougher than even pessimists expected. North Korea has seldom been more isolated, as the shots exchanged across the border yesterday emphasised. Its economy remains highly dysfunctional, and its one ally is China. Even China privately declares weariness with what it views as the highly unpredictable actions of its dangerous neighbour. But two visits this year by North Korea's leader, Kim Jong-Il, to Beijing only show how much influence China has.

Kim himself may well be running out of time. After much waiting and speculation, his third son, probably in his late 20s, has been given a collection of army and government positions, indicating that he will replace his father.

No one can ignore the problems this country of only 21 million people represents. It would create a geopolitical headache, with China and the US in particular vying for their own specific interests. China does not want a US protectorate (as it sees South Korea) unify with the North. The US would be loath to see China create an overt client state run from Pyongyang.

For the South Korean government, the objective is coldly pragmatic. The optimism of a decade ago has gone. It regards North Korea as failing to keep its promises, playing around with outside partners, and creating problems to maintain its unsustainable system. Obtaining nuclear capacity was only the worst of its many contraventions of international agreements. It regards South Korea as dangerously unstable and threatening. Any moves it makes, towards talks, more reconciliation, and commercial engagement, will be slow and highly sensitive.

The author is a Research Associate at the Centre for International Studies at SOAS