The turning point came last month, when police arrested a lawyer by the name of Marie-Helene Mattei at Bastia airport in northern Corsica. Since then, all but one of the leaders of A Cuncolta Naziunalista, the political wing of the island's main separatist movement, the Front for the National Liberation of Corsica (FLNC), have been detained.
Francois Santoni, the national secretary of A Cuncolta, turned himself in within 48 hours of Ms Mattei's arrest - she is his girlfriend and, in the quasi-feudal code of Corsican nationalism, he presented his surrender as a matter of honour. Jean-Michel Rossi, the editor of Cuncolta's magazine, was captured soon afterwards.
Along with Ms Mattei, they were transferred to Paris and charged with extortion and other offences. A dozen or so more junior activists have also been detained. In Corsica, reports of police raids on the homes of presumed nationalists have taken over from reports of small-scale bombings and strafings as the staple of daily news bulletins.
After a month of moving slowly but systematically, the authorities in Paris exude quiet satisfaction: A Cuncolta Naziunalista has been effectively beheaded and, against all predictions, there has been no bloodbath and no general strike on the island. Attacks on the mainland have become fewer and further between.
The only A Conculta leader still at large is Charles Pieri, secretary for upper Corsica, but he may be less of a threat than his awesome reputation suggests. He was badly injured in a car-bomb attack last summer and his capacity to lead the movement cannot be taken for granted.
What is unclear is whether Ms Mattei's arrest was just a lucky break for the authorities or whether - as is claimed on her behalf - she and Mr Santoni were "set up" in an elaborate operation masterminded from Paris.
The specific offence with which she and Mr Santoni are charged concerns the destruction of the guardhouse at the Sperone resort and golf club in southern Corsica. The house was blown up by a masked gang on 12 December after the resort's owner, a Paris-based businessmen named Jacques Dewez, refused to comply with a demand for protection money and - in an act almost unheard of in Corsica - went to the police.
Planned or not, the stand of Mr Dewez was a godsend for the authorities. Not only did it give them the lead to Ms Mattei and Mr Santoni, it also allowed them to present A Cuncolta as a band of common or garden gangsters, thus stripping it of its political mythology.
Opponents of the nationalists in Corsica have long accused the authorities in Paris of making secret deals with the nationalists for the sake of an uneasy peace. That excuse for a policy now seems to have been abandoned.
"I believe that we have at last left ambiguity behind," the French Prime Minister, Alain Juppe, said recently on television.
A crackdown in Corsica had been signalled ever since Jacques Chirac became president and Mr Juppe prime minister. Both insisted that it was unacceptable for there to be one law for mainland France and another for Corsica, given that Corsica is constitutionally a part of France.
For more than a year, however, such statements seemed like wishful thinking or even deliberate disinformation. Just how remote they were from the truth was revealed last October, when Francois Santoni claimed that he had had secret talks with members of Mr Juppe's staff and that Mr Juppe's office had set the terms for an armed show of strength by the nationalists the previous February - charges that were not denied.
The reasons for the policy change remain unclear. Did the bomb in October at the town hall in Bordeaux - where Mr Juppe is mayor - and the personal threats against him cause the Prime Minister to change his mind? Was it simply that the public mood on Corsica was judged to have turned against the nationalists and so offered an opportunity for change?
Whatever the reasons, the government's words and deeds now seem to be in kilter for the first time. With several former untouchables in prison on the mainland, the authorities have a freer hand to tackle Corsica's desperate economic problems. Measures to establish Corsica as a partially tax-free zone and inject new agricultural subsidies are in train as Paris tries to seize back the initiative from the island's entrenched, but invisible warlords.