The deaths of two British soldiers on 15 January and the attacks on government buildings in Kabul three days later were a reminder of the challenges of the campaign in Afghanistan. Last year, the NS warned that Afghanistan risked becoming another Vietnam, with western forces bogged down in an unwinnable war and waning popular support at home. I take the warning seriously. But I don't accept the thesis.
The conflict in Vietnam was the product of a world divided by the cold war. The UK and its European partners did not join the US in Vietnam, unconvinced by the arguments for intervention. By contrast, the intervention in Afghanistan was triggered by a direct attack against the US on 11 September 2001. It has commanded widespread global support since then and the rationale for our continuing effort remains a direct concern about the threat to our national security if Afghanistan once again becomes safe ground for al-Qaeda under the umbrella of the Taliban.
The Vietcong were a broad, deeply rooted, popular movement tapping into nationalist feelings throughout the country and society, and their appeal and legitimacy ultimately proved superior to that of the South Vietnamese regime. The Taliban have limited appeal due to their ethnicity, geography and the recent memory of their brutal, reactionary misrule. Afghans fear their return. They worry that when coalition troops begin to leave, the Afghan government will be too weak to stand up to the Taliban. That is why international troops are focusing on building up the Afghan army. It is now 100,000-strong, on the road to 134,000 in the course of this year.
General McChrystal is getting international forces not just to train Afghans, but to fight alongside them - there is no quicker or better way to build the expertise of the army than learning side-by-side in theatre.
To remain resistant to Taliban intimidation, Afghans need to know that their government can provide basic justice and maintain order. This is especially relevant as the Taliban seek to offer an alternative to the state. They appoint their own shadow governors and administer their own crude brand of "justice". The danger is that, rather than being outgunned, the Afghan government is outgoverned.
So it must build on and implement President Karzai's promise to tackle corruption. Provincial and district governors need to be given more power to govern and reach out to communities. That will include working with shuras of local elders to resolve disputes and expand social and economic provision. One example, in Helmand, is Governor Gulab Mangal's wheat distribution programme, supported by the UK, which has helped more than 35,000 farmers to grow wheat for the open market instead of opium poppies, the profits from which fill the Taliban coffers.
The enemy we face in Afghanistan is a diffuse network of insurgent groups with diverse motivations. The Taliban leadership is linked to al-Qaeda. The great mass of fighters is not. Most are driven by pride or the pursuit of profit or power rather than ideology.
Where the Vietcong were unified, the insurgency is a coalition of convenience that is capable of being divided. In his inauguration speech, President Karzai committed to an open and inclusive settlement for Afghanistan, beginning with a peace jirga - a gathering of the leaders of tribes and groups that make up Afghan society. We must support the government in its efforts to draw conservative Pashtun nationalists away from the insurgency. We must separate those who are prepared to participate in the free and open society enshrined in the Afghan constitution from the hardline ideologues whom we must face on the battlefield.
Neighbouring countries are suffering from the terrorism, drugs and crime that spill over Afghanistan's borders. As a result, it is becoming increasingly clear within the region that a stable, sovereign Afghan state is in the interest of all its neighbours. We need to build trust between these countries about each other's intentions. Pakistan is key. The history of finger-pointing (at best) with its neighbour has been replaced by co-operation. The Pakistani army's offensive in the Federally Administered Tribal Areas means that the Taliban are being squeezed on both sides of the border.
The implications for how we succeed are clear: military and development resources are critical, but they need to be channelled towards a clear political strategy aimed at maintaining the support of the Afghan people, dividing the insurgency and building regional co-operation. That is the task when more than 70 countries and international organisations meet in London on 28 January to discuss Afghanistan. We will be looking to President Karzai's government to show that its intentions on security and governance will be carried through into action. And the international community must renew and redouble its commitment to success.
This is a critical year for Afghanistan. The tempo of operations will increase - so, too, the resources. We are not trying to build a colony for ourselves. We are trying to prevent it becoming a crucible once again for attacks against the rest of the world. This is a necessary and achievable goal.
David Miliband is the Foreign Secretary and MP for South Shields