It would be​ hard to imagine a less likely political martyr than Boris Nemtsov. He was loud, brash, boastful, vain and a tireless womaniser. My favourite story about him came from a Moscow journalist who once shared a cab with Nemtsov and a photographer whom he’d been wooing to no avail. It was late at night and he fell asleep. The photographer was the first to be dropped off, and Nemtsov suddenly woke up. ‘So what do you say?’ he asked. Receiving another no, he went back to sleep.

Nemtsov was a young physicist in Nizhny Novgorod when perestroika began. He got involved in protest politics and was elected to the first democratic Supreme Soviet in 1990, associating himself with the anti-Soviet, ‘democratic’ wing. He caught Boris Yeltsin’s eye and was appointed governor of Nizhny Novgorod. After six years with mixed results, he was called back to the Kremlin to join the cabinet of ‘young reformers’ who, it was claimed, would renew economic progress for Yeltsin’s second term. Nemtsov was the most handsome among them, and a physicist, and Jewish! Looking at photos of him with Yeltsin, who sometimes presented Nemtsov as his successor, one couldn’t help but be filled with hope. Then Nemtsov opened his mouth. The first time I saw him on TV was during a celebration of the ageing pop singer Alla Pugacheva; he reminded her that she’d once said she liked sleeping with her husband because he reminded her of Nemtsov. It was a strange performance for the future hope of Russian democracy.

I spent a week with Nemtsov many years later, in 2009, when he was running for mayor of Sochi. He was still amazing. It was early spring in Russia and yet Nemtsov had a full tan. Everywhere we went he wore blue jeans, a black jacket and a white shirt with the top three buttons undone. He addressed everyone he met with the familiar ty, which was rude, and he hit on all the women journalists. But he was totally committed to what he was doing, and bizarrely, bull-headedly, fearless. By this point he had started publishing short, well-researched reports about corruption in both the presidential administration and the Moscow mayoralty. Later he would publish one about construction of the various Olympic sites in Sochi. Whoever he was speaking to he would say: ‘Have you read my book about that? You need to read my book about that.’ And he would start making arrangements to send them a pamphlet.

His campaign in Sochi was quixotic. This former governor and deputy prime minister, ten years out of government, was travelling around in a rented yellow minivan, trying to get people on the street to talk to him. Most of them recognised him, he was a celebrity, but they weren’t about to stick their necks out for him. His rallies were poorly attended. His volunteers put up posters with his handsome face only to find they’d been torn down overnight. (The Kremlin had agreed to let him register his candidacy but had no intention of letting him win.) He was subjected to relentless attacks on his character in the local and national media. A group of young men, who for some reason were wearing dresses, splashed ammonia on him before a press conference.

On my first night in Sochi, Nemtsov and the former chess champion turned oppositionist Garry Kasparov, who was helping him on the campaign trail, attended the birthday party of a local teenager. Then they spent hours drinking and kibitzing with her parents. Nemtsov was furious that the local governor, Alexander Tkachev, who was presumably in charge of most of the harassment directed at his campaign, could treat him so shabbily. ‘You’re from New York,’ Nemtsov said at one point, turning to me. ‘Who is more popular in New York, Nemtsov or Tkachev?’ The answer was Nemtsov, but we weren’t in New York.

Nemtsov’s time as deputy prime minister in the cabinet of ‘young reformers’ had been a catastrophe. The main characteristics of Russia’s post-Soviet system had been put in place by Yeltsin and the previous set of reformers: extraordinary powers for the president; a purely decorative parliament; much of the industrial and oil wealth of the country in the hands of a few well-connected businessmen. Nemtsov and the others declared that they were undertaking another round of ‘shock therapy’ and tried to raise the alarm about the oligarchs. It didn’t work out well. After more than a year of chaos, Russia defaulted on its treasury bonds. The ruble collapsed and Nemtsov and the others were out. ‘Russia needs to enter the 21st century with only young people,’ Nemtsov had said shortly after coming to Moscow. On New Year’s Eve 1999, Yeltsin would use almost exactly the same words to introduce his chosen successor, Vladimir Putin.

The terrible state of Russia’s economy and its institutions wasn’t entirely Nemtsov’s fault, but he refused, along with almost all the rest of his cohort, to reflect on what had gone wrong in the 1990s. Asked if things should have been done differently, he would say that fixing the presidential election in 1996 had been a mistake, ‘a bad omen’. But he didn’t question the actual reforms, the haste and brutality with which they were undertaken, or the fact that they created a small class of successful post-Soviet winners (like Nemtsov) and a much larger underclass of forgotten and discarded losers. Instead he blamed everything that went wrong in the next 15 years on Putin. ‘When is that bastard finally going to go away?’ he said in Sochi in 2009. ‘When?’

He was wrong to hold Putin responsible for all of Russia’s problems, but the error kept him going. By the time of the Sochi election, most of the other ‘young reformers’ had either gone into academia or accepted technocratic positions in the Putin administration; later apostates assumed more or less quiet positions in the opposition. But Nemtsov not only remained active, he was tremendously outspoken. And most of his anger was directed squarely at Putin. The reports he wrote included Putin: A Summing-Up; Putin and Gazprom; Putin and the Financial Crisis; Putin and Corruption. The next report was going to be about Putin and the war in Ukraine.

The reports were neither groundbreaking nor particularly well written; they tended to rely on published accounts from open sources. But they were always well publicised, and their way of gathering the known facts, as well as their association with Nemtsov, meant they were useful as agit-prop tools. More than anything there was the incongruity of it. If you had asked in 1998 who of the 1990s politicians would 15 years later still be going out and protesting, getting arrested, publishing critical reports and putting himself in danger, I don’t think anyone would have said Nemtsov. And yet Nemtsov was the one – the only one.

Russians have witnessed so many killings of regime opponents in the past twenty years that it’s become one of their chief areas of expertise. When Putin’s press secretary, the soft-spoken, bewhiskered Dmitry Peskov, said after the killing of Nemtsov that the Kremlin couldn’t have had anything to do with it because Nemtsov wasn’t an influential politician, people were reminded of what Putin had said immediately after the journalist Anna Politkovskaya was killed. ‘Her influence over political life in Russia was minimal. Murdering such a person certainly does much greater damage from the authorities’ point of view … than her publications ever did.’ Seven years later, Peskov on Nemtsov: ‘In political terms he did not pose any threat to the current Russian leadership or Vladimir Putin. If we compare popularity levels, Putin’s and the government’s ratings and so on, in general Boris Nemtsov was just a little bit more than an average citizen.’ This was grotesque. It made them sound guilty. And yet it almost made them sound innocent too. Wouldn’t the cold-blooded murderers of a political opponent have the good sense simply to express their sadness at the loss and leave it at that? Maybe. But then again, if these guys had been geniuses, they’d have done a lot of things differently.

By comparison to the previous killings, a few things stand out. One is the bizarre proximity to the Kremlin: Nemtsov lived across the river from Red Square, so it wasn’t a strange place for him to be, yet surely there were less obvious places where he could have been shot – places where no one would have been able to take photos of his body with St Basil’s Cathedral looming in the background. Another was the remarkable level of efficiency. A security camera captured the entire event from a distance, and it happened with great speed. The killer fired six rounds, four of them on target, then jumped into a car which pulled up at that moment and whisked him away.

That the killing was a highly professional job doesn’t necessarily mean it was ordered by the highest professional. We don’t know much about the way the Kremlin works. We know that there are things Putin doesn’t like to be asked about: they’re too small-time. But we also seem to know that there are things Putin demands to be in charge of. It’s just hard to know which category a thing falls into. The difficulty of telling the difference must account at least in part for the ineffectiveness of the Putin regime.

The biggest difference between this killing and the many others that preceded it was Nemtsov’s prominence. The journalists Dmitry Kholodov, Paul Klebnikov, Politkovskaya, the human rights activist Natalia Estemirova, the Duma deputy Galina Starovoitova: none was so immediately recognisable to so many people; none had once been so high up in government. None had been labelled enemy number one by the nationalists and other pro-Kremlin activists who have emerged as if from a time warp to take up the banner of the war against Ukraine. That war was Nemtsov’s finest moment. On 2 March 2014, when it first became clear what was happening, Nemtsov wrote a furious article which the liberal radio station Ekho Moskvy refused to post on its site unless he took out some of the more inflammatory language. So he posted it on Facebook instead:

Putin has declared a war of brother against brother in Ukraine. This bloody folly by a crazed KGB man will cost Russia and Ukraine dear: once again the deaths of young boys on both sides, bereft mothers and wives, children turned into orphans. An empty Crimea, which tourists will never visit. Billions, tens of billions of rubles, taken from old people and children and thrown into the furnace of the war, and then after that even more money to prop up the thieving regime in Crimea … The ghoul needs a war. He needs the blood of the people. Russia can look forward to international isolation, the impoverishment of its people, and repressions. God, why should we be cursed like this??? How much longer can we take it?!

It was a remarkable performance from someone who could long since have retired from politics. Nemtsov enjoyed windsurfing and paragliding in places like Venezuela – hence his nice tan. He could have moved to New York like his friend Kasparov.

Ukraine has been the question hanging over the Putin administration since 2004. In the minds of Putin and his people, it’s the final battle. If Ukraine can be kept out of the hands of the West, Russia wins. If it joins the EU and Nato, Russia is effectively reduced to borders not seen since the time of Peter the Great. What’s puzzling is that Nemtsov’s murder took place just two weeks after Russia to all intents and purposes won the war. At the negotiations in Minsk, Ukraine effectively surrendered. It had already fallen into chaos. The government is unpopular, the volunteer battalions have minds of their own, and the economy is in ruins: we’ve heard a lot from Western politicians about the collapse of the Russian currency (it’s lost 50 per cent of its value over the last year), but less about the collapse of the hryvnia, which has gone from eight to the dollar before Maidan to 24 to the dollar today. If, as most believe, Putin’s goal, if he couldn’t have Ukraine, was to destabilise it, he’s achieved it. But the price appears to have been Russia’s domestic tranquillity. The general mobilisation in support of the president has taken increasingly ugly forms. In December, in the stadium in Grozny in front of thousands of armed men, Ramzan Kadyrov put himself and his troops forward as the president’s special volunteer battalion. ‘We know that the country has an army, a navy, an airforce and nuclear capabilities,’ he said, ‘but we also know that there are some missions that can only be accomplished by volunteers.’ Two months later, a week before Nemtsov’s murder, a biker gang called the Night Wolves led a big meeting in Moscow called Anti-Maidan, with the slogan, ‘There won’t be a Maidan in Russia.’ Ukraine has lost the war, but what the war has done to Russia may be even worse.

For years now there has been speculation about a ‘party of war’, which periodically stages provocations in order to push the president into decisive action. The party of war was said to have manoeuvred Yeltsin into Chechnya and, more conspiratorially still, to have blown up the apartment buildings in Moscow in 1999 to push Putin into Chechnya in his turn. The party of war may also have sent Igor Strelkov and his merry band of murderers into eastern Ukraine last spring, to turn an inchoate set of local protests into the beginnings of a civil war. But does the party of war actually exist? We’re unlikely ever to know, even after all the archives have been opened and all the email accounts hacked. It is, however, a useful concept, even if its only function is to describe one part of Putin’s mind that’s in dialogue or competition with another. It would explain why Putin sometimes goes forward and sometimes steps back. And it gives at least a small space for hope, since if there’s a party of war there is also, presumably, a party of peace, and it might just win.

I always thought that Nemtsov would make it, that he would be shielded from the vengeance of the system in part because he was Nemtsov. He had a PhD in physics, but he wasn’t a serious thinker, nor did he pretend to be one. You could never tell if he was speaking out because he believed what he was saying or because he couldn’t stand being ignored. Or if he kept getting arrested at opposition rallies because he considered it an act of conscience or because he liked getting his picture taken (sometimes, when they arrested him, the police tore his shirt, and you could get an extra glimpse of his tan). Did he hate Putin because of what he’d done to the country, or because he felt cheated out of his birthright by their shared mercurial surrogate father, Boris Yeltsin? He was a narcissist, and there was his way with young women. On the last night of his life, he went with his girlfriend, a Ukrainian model called Anna Duritskaya, to a nice restaurant in the upscale mall just across Red Square from the Kremlin. Then they walked in the rain across the bridge towards his apartment.

Who knows why people do the things they do? Who knows why Nemtsov kept fighting for some kind of change in a country to which he himself had brought a lot of pain? And neither do we know exactly why they killed him. But it’s clear that it wasn’t for his human flaws, or for his contribution to the economic catastrophe of the 1990s. He was killed for his opposition to the war. Since the start, critics have been warning that the war in Ukraine would eventually come home to Moscow. No matter who pulled the trigger on the bridge, it has.