On the 20th anniversary of the West’s war in Iraq, progressives in the UK will remember the important moment in 2003 when millions stood up to an unjust invasion and said: “Not in our name.”

Yet more than a year into Russia’s war against Ukraine, this is also a moment of nuance. Today, progressives in the West have made a crucial distinction between their own country’s imperialist wars and another democracy’s war of self-defence against imperialism.

This distinction has not come easy.

The West has long been divided about the very concept of war. Its Indo-European root word means confusion and discord, but war is also seen as valorous and honourable in the defence of something most valued. War is driven by something that really matters being at stake. Yet it is shaped by means that are inherently destructive, unruly and hard to contain.

This confusion applies to the very real risks posed by Vladimir Putin and his nuclear-capable oligarchy – and the sceptical view that progressives rightly take of our own government and its economic and geopolitical motivations for supporting Ukraine’s resistance. That’s a challenge.

As progressives, all wars should sit uncomfortably with us. I know I’ve found it uncomfortable – I still do, even now. When I put down an early day motion in Parliament, demanding more weapons be sent to Ukraine, I agonised over it. I’ve been torn by it.

But it’s OK to be torn, to doubt ourselves. The waging or supporting of war should never come easy to us. The world, after all, rarely fits into a narrative of absolute good and evil.

On the UK’s support for Ukraine, I didn’t want to see more money and power put into the hands of arms dealers and the military industrial complex. I didn’t want to find myself on the same side in Parliament as the Tories and other assorted warmongers.

But I understood my political misgivings. My discomfort was nothing compared to the existential fight and the sacrifices Ukrainians have made and continue to make to defend their homes, their families and their democracy from brutal, naked aggression. I understood, as complex as it is, that supporting the Ukrainian people in their hour of need was, and is, the right thing to do.

Contrary to what some on the left think, the fact I served in the British Army doesn’t make me more prone to militarism or imperial adventurism. For me, it actually works in the opposite way. It makes me even more wary.

While I don’t regret the vast majority of my personal experiences in Afghanistan in 2009, I do regret Western motivation for the intervention itself. It saw me and thousands of others serving in Afghanistan. It wasn’t Iraq but, in hindsight, I believe it failed the litmus test of a just war.

Britain’s Afghanistan invasion was ill thought through. Ultimately, it fell victim to the paradox of security in which the more arms and troops we poured into Afghanistan, the stronger the enemy became. It was a military intervention that fostered a spiral of violent regression and ever greater instability.

If you doubt that, then simply look at the violence and chaos that now engulfs Iraq, Syria and Afghanistan. They are a grim warning about the current Western approach to the issue of global security, which is still a one-size-fits-all militarism.

If you’ve seen the consequences of war, you would not be keen to see it repeated. Mutilated civilians. Mentally broken soldiers. People you speak to one day are gone the next. That is why millions of people, 20 years ago, came out in their millions against the Iraq war.

Russia’s war against Ukraine is different. Its conclusion is as yet unknown.

Putin has implied that Russia would be prepared to use nuclear weapons if NATO were to interfere excessively in Ukraine. What that looks like, nobody knows. But it means that Joe Biden – and by default the UK, which is closely shadowing the US on this issue – is unlikely to provide the longer-range weaponry that would allow Ukraine to go on the offensive in Crimea, which Russia has occupied since 2014.

NATO planners – who, like Russia, have a first-strike doctrine – must surely be aware of this danger. That means there are limits to our support for Ukraine in terms of weaponry. It cannot be a blank cheque. But nor should it be a drip-feeding of ineffective, insufficient military support that cynically uses Ukraine and its people to weaken Russia.

The peace we build after the conflict in Ukraine has concluded – and it will – must be sustainable. Ukraine’s economy must be closer to Finland than the US. An unequal, privatised, authoritarian Ukraine will be far more likely to shift to the authoritarian right. That could yet see it fall into the orbit of an increasingly right-wing and authoritarian Russia, as in the case with Belarus. Or it could have an authoritarian and nationalist regime intent on antagonising and provoking its larger neighbour. That would have consequences for all of us.

But there is also another way and one we must consider if we are to deal with the other crisis in the room: climate change.

A growing body of evidence suggests there are strong links between climate and conflict around the world. The effects of climate change, such as changes in temperature and precipitation, can increase the likelihood and intensity of conflict and violence. Climate change, then, is a threat-multiplier.

An influential 2015 paper found that changes in temperatures and precipitation patterns increase the risk of conflict: every 1°C increase in temperature increases conflict between individuals (for example, assault, murder) by 2.4% and conflict between groups (riots, civil war) by 11.3%.The implications are clear – that global security will deteriorate even more dramatically this century.

Contrary to popular belief, the Global Green New Deal – backed by legislators across the world – isn’t just about building more wind turbines and planting more trees, critical as these are. It is the implicit understanding that the only way we will navigate this century is to make our own country and the world less unequal in terms of power and wealth.

That redistribution of wealth – from Global North to South via reparations, technology transfers and trade deals – won’t happen if we continue with emaciated institutions and crumbling democratic apparatuses both here in the UK and internationally. The climate crisis is as much a failure of democracy as it is markets.

The Ceres2030 research group, an international research coalition, has estimated that it would be possible to achieve the goal of zero hunger by 2030 at a cost of $330bn. Compare that to the world’s annual military spend of £1,917bn.

This is where Finland as a model for Ukraine comes in. Universal welfare, lower inequality and more robust democratic practices would lead to enhanced social trust and community cohesion.

It is this kind of security in depth – but on an international scale – that is required now. Simply, responding to the unfolding chaos with ever greater military support will create an increasingly destructive feedback loop.

This article is based on remarks given at the Solidarity with Ukraine: Building a New Internationalism conference at the London School of Economics, March 2022.