Who are Eta?
For more than three decades the armed organisation Eta has waged a bloody campaign for independence for the seven regions in northern Spain and south-west France that Basque separatists claim as their own.
Euskadi Ta Azkatasuna, Eta, whose name stands for Basque Homeland and Freedom, first emerged in the 1960s as a student resistance movement bitterly opposed to General Franco's repressive military dictatorship.
Under Franco the Basque language was banned, their distinctive culture suppressed, and intellectuals imprisoned and tortured for their political and cultural beliefs.
The Basque country saw some of the fiercest resistance to Franco. His death in 1975 changed all that, and the transition to democracy brought the region of two million people home rule.
But despite the fact that Spain's Basque country today enjoys more autonomy than any other - it has its own parliament, police force, controls education and collects its own taxes - Eta and its hardline supporters have remained determined to push for full independence.
Its violent campaign has led to more than 800 deaths over the last 30 years, many of them members of the Guardia Civil, Spain's national police force, and both local and national politicians who are opposed to Eta's separatist demands.
Nonetheless, their power was thought to have faded significantly in recent years; although debate has raged as to whether the group was a spent force or simply lying in wait.
Waning support
Certainly the days in the late 1970s, when the group was able to kill 100 people per year on average - just as Spain was awakening from a long dictatorship and moving towards democracy - appeared to be over.
After three people were killed in 2003, Eta refrained from any other deadly attacks until the last days of 2006.
The Eta of today has some logistical networks in France and a pool of a few hundred youths scattered across the borders of the Basque Country, in France and Spain, willing to engage in deadly missions.
French and Spanish police have sought to reduce Eta's capability and the Spanish government and judiciary have banned the political wing of the movement, which seeks an independent state for the Basques.
The logic for banning the political wing, which has operated for the last decade under different names - Herri Batasuna, Euskal Herritarrok, Batasuna - is that both wings are inextricably linked.
Banning the political branch, it was hoped, would reduce the flow of funds and support to Eta units.
No-one knows just how big the covert organisation is but the Spanish authorities estimate those active in Eta, fully paid up members who are trained to kill and who work in cells of around four people, could number as few as 30.
No wonder then, that they hailed the raids in Spain and France in October, resulting in the seizure of huge caches of arms and the arrest of more than 20 suspects, as a significant blow to the organisation.
A particular coup was the arrest of suspected Eta leader Mikel Albizu, also known as Mikel Antza, and his girlfriend, Maria Soledad Iparraguirre.
There has also been less and less backing for Eta and its extremist followers. This is not only because of the gains made in recent years by moderate Basque nationalists, but also because there is a growing feeling that Eta is desperately out of touch with public opinion.
Changing times
Eta's July 1997 kidnapping of a 29-year-old local councillor for the ruling Popular Party in the Basque region, Miguel Angel Blanco, was a turning point in public opinion.
Eta attacked two hotels in 2003
The group demanded that, as a prerequisite for his release, its 460 prisoners who were held in jails all over Spain be returned to the Basque region. The demand was not met.
Blanco was found shot twice in the head, he died in hospital 12 hours later.
Horrified by the young councillor's death, more than six million people across Spain took to the streets over four days to demand an end to Eta violence.
The massive public mobilisation was likened to the marches for democracy that took place towards the end of Franco's regime, and in an unprecedented move some of Eta's own supporters publicly condemned the killing.
The following year, Eta decided to call an indefinite ceasefire.
But that was officially ended in December 1999 after the then government refused to discuss Eta's demands for Basque independence.
The Spanish government had always maintained it would never consider entering talks with the armed group unless it renounced violence.
The Popular Party campaigned for re-election in part on its tough line against Eta and its defence of Spain's constitution in the face of demands for greater autonomy from the Basque country and Catalonia.
But 11 March 2004 bomb attacks in Madrid introduced a new factor in the equation.
The Popular Party initially said the attacks were the work of Eta, although the finger of blame soon moved to point at Islamist groups.
The electorate rejected the government and voted in the Socialist Party, partly because the Popular Party was perceived to have misled them.
Eta attacks declined in the wake of Madrid bombings, as the group was thought to believe it could no longer achieve its aims by violence.
Eta set off a number of bomb devices to coincide with national holidays and strikes, but no-one was killed.
The group finally declared a ceasefire, describing it as permanent, in March 2006.
However, the bombing of a car park at Madrid airport in December of that year left two people dead, and prompted the government to call off peace talks.
