I still remember the images from the fall of Saigon in 1975. Following the withdrawal of American forces from South Vietnam in 1973, the Spring offensive by the forces of North Vietnam in 1975 led to the fall of Saigon in April that year, and the subsequent re-unification of Vietnam under a communist government.

The key images I remember were a North Vietnamese tank smashing its way into the presidential palace and desperate people scrambling to get a place on the last helicopters trying to evacuate people from the roof of the American embassy.

Listening to a report about the deteriorating military situation in Afghanistan on the radio this morning I wondered if we will shortly be seeing similar scenes being played out in the Afghan capital Kabul.

Following the Doha accord agreed by the United States and the Taliban in February 2020, all NATO forces are due to leave Afghanistan by 11 September this year, but the vast majority have now already been withdrawn. As a UK Parliamentary briefing paper notes:

....There has been a spate of targeted killings of prominent figures in civil society, the media, judiciary and civil administration, most notably among women. In recent weeks the Taliban has begun a major offensive against Afghan government forces as the summer fighting season begins. Dozens of districts have fallen to the Taliban, particularly in the north, with reports of little resistance by the Afghan National Security Forces. Hundreds of Afghan soldiers have fled across Afghanistan's borders into neighbouring Tajikistan. Recent heavy fighting between Afghan and Taliban forces in Helmand, Kandahar and the northern provinces has also forced thousands of Afghan civilians to flee their homes.

The paper goes on to explain that there seem to be two likely scenarios for the future. The first is that the Taliban will achieve a military victory, and that a Taliban regime will take over Afghanistan just as a communist regime took over South Vietnam. The second is there will be a full scale civil war, with neighbouring powers supporting those factions who are perceived to be favourable to their interests.

Both of these outcomes will have dire consequences for the people of Afghanistan, who have already suffered from decades of war, repression, and political instability, and will lead to a new wave of refugees fleeing the country, just as the 'boat people' fled Vietnam after 1975.

Reflecting upon the news from Afghanistan led me to think about what the NATO withdrawal looks like from the standpoint of Christian just war theory.

Christian just war theory is based on the teaching of Romans 13:1-7 that God has given governments the authority to use force in order to execute the justice of God in the face of human wrongdoing. In this context, war is seen as being, in the words of Anglican academic Oliver O'Donovan, "an extraordinary extension of ordinary acts of judgement."

That is to say, just as governing authorities normally take action by means of the policing and judicial systems of their countries to enact the justice of God in response to various forms of injustice, so also, on occasion, they have to resort to war for the same reason. In this view, war is permissible as a means of seeking to achieve justice in response to some form of grave injustice that would otherwise continue.

According to Christian just war theory, for a war to be just, and therefore in accordance with God's will there has to exist both 'the right to go to war' (jus ad bellum) and 'right conduct in war' (jus in bello).

For the first of these criteria to be met, a war has to be declared and waged by the governing authorities mentioned by Paul in Romans 13:1-7 and by Peter in 1 Peter 2:13-14. In addition, these governing authorities must be waging war for a just cause, namely, to prevent or correct some form of injustice that could not be prevented or corrected in any other way. There also has to be a reasonable chance of success. If a war cannot be won, then there is no chance of God's justice being furthered, and therefore no point in waging it.

For the second of these criteria to be met, everything that can be done must be done to reduce casualties among non-combatants, that is civilians and soldiers who have surrendered. What is known as the proportionate use of force states that if non-combatant casualties occur they must be unavoidable, unintentional, and kept as low as possible.

Thinking about these criteria in relation to Afghanistan, it has struck me that there is something missing from them, which is the further principle that war should not be prematurely concluded. If a war is being waged for just cause then it would be wrong to end the war while there is still a reasonable prospect of that just cause being achieved. Just as a war for unjust ends would be morally wrong, so would a cessation of war that left achievable just ends unattained.

That is what I fear is true of the NATO withdrawal from Afghanistan. The just causes for which NATO troops have been fighting since 2000 have been to prevent Afghanistan being used as a base for international terrorism, and to try to bring about as far as possible a peaceful and democratic future for the country, in which the human rights of all Afghans, and particularly Afghan women, will be properly respected.

On both of the likely scenarios for the future of Afghanistan, neither of these outcomes can be guaranteed, or are indeed likely. However, there was a realistic possibility that they might have been attained had NATO forces remained. I would argue, therefore, that in the light of Christian just war theory the decision by the Trump and Biden administrations to cut and run was an unjust one that should not have been taken.

Martin Davie is a lay Anglican theologian and Associate Tutor in Doctrine at Wycliffe Hall, Oxford.