By the West it is regarded as an act of unilateral Russian aggression that triggered a wider Ukrainian crisis. The Russian narrative remains that it was a justified reaction to the illegal overthrow of Ukraine's president by pro-Western mobs in Kiev, and the perceived threat that a new Ukrainian government could nationalize its historic naval base in the Crimean port of Sevastopol.
Moscow has paid a heavy price for its actions, with its economy sagging under the weight of Western sanctions, while Russia's image around the world has suffered a black eye over its actions in Ukraine.
But at least one group appears to be relatively pleased about the outcome: Crimeans.
A telephone poll conducted by a German firm among Crimeans in January found that over 80 percent of respondents were happy to be newly-minted Russians.
A far more rigorous survey, conducted on the ground in Crimea by two US professors working with the independent Levada Center in Moscow, arrived at nearly identical results. Despite the transitional troubles of the past year, 84 percent of Crimeans regard the annexation as "the right thing to do."
However, it also found that indigenous Crimean Tatars, who make up about 10 percent of the population, are much more opposed to joining Russia than ethnic Russians and Ukrainians. Tatars were far more likely to say that Crimea was moving in the wrong direction.
Yet the world’s view is that Russia violated Ukraine’s territorial integrity – and therein lies the conundrum. "Russia’s annexation of Crimea was an illegal act under international law [but] it is also an act that enjoys the widespread support of the peninsula’s inhabitants," the survey's authors write.
That's exactly what Russian President Vladimir Putin says he knew for sure before he gave the go-ahead to annex Crimea last year.
"We found out that 75 percent of respondents in Crimea wanted to join Russia," after conducting a secret poll, he told a soon-to-be-broadcast TV documentary. The film reveals just how deeply Mr. Putin was involved in planning the rapid and casualty-free seizure of a Ukrainian province with a garrison of 18,000 troops.
Some of the fibs dispensed by the Kremlin at the time are disposed of. Russian media staunchly claimed that the "little green men" with modern arms and equipment who seized Crimea were local people, though Putin later admitted they were actually Russian troops. The Kremlin also insists to this day that Russian-speakers – a huge majority in Crimea – were under threat, although there is little evidence of that.
"I told my colleagues that the situation in Ukraine has evolved in such a way that we have to start work on returning Crimea to being a part of Russia. We couldn't abandon the territory and people who live there, couldn't just throw them under this nationalist bulldozer,” Putin says he told an urgent Kremlin meeting on Feb. 22, 2014. Pro-Russian Ukrainian leader Viktor Yanukovych had just been overthrown.
"The ultimate goal was not to seize Crimea or annex it,” Putin said. “The ultimate goal was to let people express their opinion on how they wanted to live further.”
The operational lies told by the Kremlin at the time still divide experts.
"When the president of a country declares publicly that our army isn't behind certain events, and then we find out that our troops basically orchestrated a referendum in a foreign territory, it does tend to harm the reputation," says Alexander Konovalov, president of the independent Institute of Strategic Assessments in Moscow. "He told lies, and that led to serious violations of international law, how can that not hurt Russia's image?"
But Sergei Mikheyev, director of the independent Center of Political Technologies in Moscow, says it's no worse than former US Secretary of State Colin Powell offering false testimony about Iraqi weapons of mass destruction at the UN.
"Russia did what it had to do. It's international practice, and there's no reason to single Russia out. If we hadn't taken these steps, we might have lost our naval base at Sevastopol," he says.