In 2014 Ukraine’s “revolution of dignity” culminated in the ouster of a Russian-friendly president, Viktor Yanukovych, and this created fear in Moscow.

For Russian President Vladimir Putin the revolt in Ukraine hit too close to home. He reacted by annexing Crimea (after a referendum that violated Ukraine’s constitution), while working to foster two separatist “republics” across the border in Ukraine’s Donbas region.

A little more than a month before his invasion at a meeting of the Russia-led Collective Treaty Organisation, he warned that “we will not allow the realisation of so-called colour-revolution scenarios” and promptly dispatched 2,500 troops to Kazakhstan following a revolt there.

As for Ukraine, while it may be an imperfect democracy, it was certainly making progress. Its elections were cleaner than Russia’s and its media far freer, as political parties competed, governments were voted in and out of power, and civic groups multiplied.

All of this, so goes the argument, Putin found intolerable, fearing that such democratic ideas and aspirations would eventually make their way to Russia. As it happens, though, none of this explains the timing of his invasion. 

After all, Ukraine had been moving toward political plurality for years, however slowly and unevenly, and however far it still had to go. So, what was happening in 2021 that could have taken his fear to new heights?

The answer: nothing, really. Those who claim that Nato was irrelevant to the invasion often insist that the deed sprang from Putin’s ingrained authoritarianism, dating back to his days in Russia’s secret police, the KGB, his love of unchecked power, and his dread of uppity citizens inclined to rebellion.

The problem: none of this explains why the war broke out when it did. Russia wasn’t then being roiled by protests; Putin’s position was rock-solid; and his party, United Russia, had no true rivals. Indeed, the only others with significant followings, relatively speaking, the Communist Party and the Liberal Democracy Party (neither liberal nor democratic), were aligned with the state.

According to yet another explanation, he attacked Ukraine simply because he’s an imperialist through and through, yearns to go down in history as Putin the Great (like Russian tsars Peter the Great and Catherine the Great), and has been transfixed by far-right thinkers, above all the exile Ivan Ilyin, whose remains he arranged to have returned to Russia for reburial.

But why then did a Russian ruler seized by imperial dreams and a neo-fascist ideology wait more than two decades to attack Ukraine? And remember, although now commonly portrayed as a wild-eyed expansionist, Putin, though hardly a peacemaker, had never previously committed Russian forces to anything like that invasion.

His 1999-2009 war in Chechnya, though brutal, was waged within Russia and there was no prospect of outside intervention to help the Chechens. His brief military foray into Georgia in 2008, his landgrab in Ukraine in 2014, his intervention in Syria in 2015 – none were comparable in their size or audacity.

Do I have a better explanation? No, but that’s my point. To this day, perhaps the most important question of all about this war, the biggest surprise – why did it happen when it did? – remains deeply mysterious, as do Putin’s motives (or perhaps impulses).

Once Russian troops did cross Ukraine’s border, just about everyone expected Kyiv to fall within days. After that, it was assumed, Putin would appoint a quisling government and annex big chunks of the country. The CIA’s assessment was that Ukrainian forces would be trounced in no time at all, while Chairman of the Joint Chiefs of Staff General Mark Milley reportedly told members of Congress that resistance would fizzle within a mere three days.

Those predictions briefly seemed on the mark. After all, the Russian army made its way to the northern suburbs of the Ukrainian capital, Kyiv – think of a military bent on capturing Washington DC, reaching Bethesda, Maryland – before being stopped in its tracks. Had it taken that city, we would be in a different world today.

But – perhaps the biggest surprise of all – the far weaker Ukrainian army not have only prevented what was then considered the world’s second-greatest military superpower from taking Kyiv, but in September 2022 ejected Russian forces from the north-eastern province of Kharkiv.

That October, it also pushed them out of the portion of the southern province of Kherson they had captured on the right bank of the Dnipro River. In all, Ukrainian forces have now retaken about half the territory Russia occupied after the invasion.

As winter approached that year, the crescent-shaped frontlines extending from northern Luhansk Province (one of two that make up the Donbas region) all the way south became the scene of World War I-style trench warfare, with both sides throwing their troops into a virtual meat grinder. Still, since then, despite having overwhelming superiority in soldiers and firepower – the estimated artillery exchange ratio between the two forces has been put as high as 7:1 – Russia’s advance has been, at best, glacial, at worst, non-existent.

The Russian army’s abysmal performance has perplexed experts. According to American, British and Norwegian estimates, it has suffered something on the order of 180,000-200,00 casualties. Some observers do believe those numbers are significantly too high, but even if they were off by 50 per cent, the Russian army’s casualties in one year of fighting would exceed by perhaps twofold the losses of the Soviet Union’s Red Army during its 10-year war in Afghanistan.

Russia has also lost thousands of tanks, armoured personnel carriers and helicopters, while vast amounts of equipment, abandoned intact, have fallen into Ukrainian hands. All of this, mind you, after Putin initiated a megabucks military modernisation drive in 2008, leading the Economist to declare in 2020 that “the Russian military dazzles after a decade of reform” and Nato had better watch out.

For the surprising evolution of the war, unlike so much else, I do have an explanation. Military experts typically dwell on what can be counted: the level of military spending, the number of soldiers, tanks, warplanes, and artillery pieces a military has, and so on. They assume, reasonably enough, that the side with more countable stuff is likely to be the winner – and quickly if it has a lot more as Russia indeed did.

There is, however, no way to assign numerical values to morale or leadership. As a result, they tend to be discounted, if not simply omitted from comparisons of military power. In Ukraine, however, as in the American wars in Vietnam in the last century and Afghanistan in this one, the squishy stuff has, at least so far, proven decisive.

French emperor Napoleon’s dictum that, in war, “the moral is to the physical as three to one” may seem hyperbolic and he certainly ignored it when he led his Grande Armée disastrously into Russia and allowed the brutal Russian winter to shred its spirit, but in Ukraine – surprise of surprises – his maxim has held all too true, at least so far.

When it comes to surprises, count on one thing: the longer this war continues, the greater the likelihood of yet more of them. One in particular should worry us all: the possibility, if a Russian defeat looms, of a sudden escalation to nuclear war. There’s no way to judge or measure the probability of such a dreaded dénouement now. All we know is that the consequences could be horrific.

Although neither Russia nor the United States seeks a nuclear war, it’s at least possible that they could slide into one. After all, never, not even in the Cold War era, has their relationship been quite so poisonous, only increasing the risk of both misperception and overreaction born of worst-case thinking.

Let us hope, in this war of surprises, that it remains nothing more than another of the scenarios strategists like to imagine. Then again, if as 2021 began, I had suggested that Russia might soon invade Ukraine and begin a war in Europe, you would undoubtedly have thought me mad.

• A TomDispatch report