Its lessons are simple. If we want to stop terrorists from murdering us and from dictating how we lead our lives, we must confront them. Some think the solution is to sue for peace, to negotiate with terrorists so that they might go and kill elsewhere. But that way is unacceptable to me and to millions of Spaniards. Terrorism deserves only to be defeated. This is the debt we owe to the victims of the attacks, and to the society that mourns them.

In the hours that followed the attacks, our investigation focused on one obvious suspect, the Basque terrorist group ETA. It was a reasonable inference to make, and those who say otherwise are being either naive or dishonest. History has left us with clear evidence of ETA's sinister habit of killing during election campaigns. The terrorists always attempt to soak our democracy in blood on the days when we Spaniards go to the polls to reaffirm our liberties.

ETA has committed more than 800 murders, among other crimes, over three decades, and has sought always to weaken and divide our democracy, which has just celebrated its 25th anniversary. A few days earlier, the group had tried to carry out an attack with 500 kilograms of explosives, one that failed only due to the intervention of the Guardia Civil, the national police. Those detained in this failed attack had a map that highlighted the zone of the Henares Pathway, through which run the trains that were targeted on March 11. And it was ETA that, on Christmas Eve, attempted another slaughter at Madrid's Chamartin station, also thwarted by our National Police. And to continue the ghoulish catalog, the same terrorist group brought two vans loaded with more than 1µ tons of explosives to Madrid in December 1999. Once again, our security forces foiled what would have been mass murder.

My government was not alone in attributing the March 11 attacks to ETA. In the first few hours, the president of the Basque Autonomous Region, the secretary general of the Socialist Party, the general coordinator of the United Left and the secretary general of Catalonia's Esquerra Republicana, among others, did likewise.

Although ETA continued to be our prime suspect, we did not dismiss any evidence pointing elsewhere. This is what I explained in my public appearance on March 12, the day after. Apart from the tape, which was of a commercial nature and had no immediate terrorist connotation, there were only very dubious messages from groups taking responsibility. All these fragments of evidence needed to be examined with the utmost attention and precaution.

As soon as there were signs of other possibilities besides ETA, the government placed them before our citizens. On the very night of the attack, all of Spain knew what course the investigation was taking. On Saturday, Spaniards were informed of all arrests made by the police. The government revealed all that it reasonably could reveal without jeopardizing the investigations.

And yet all these efforts at transparency and disclosure were derided as manipulation by our opponents, who, furthermore, accused us of lying about what we knew. Ignoring the chronology of events, as well as the government's efforts, some of our opponents invented a parallel reality, accusing us of a "coverup" even though the government was keeping the public informed, practically in real time, of all the evidence available and of the course of the investigation. Those who twisted the facts in this way cannot feel very proud today. Instead of backing the government during the worst crisis in Spain's recent history, our opponents declared that truth and transparency were on their side.

ETA or al Qaeda--the difference is important, to be sure, but the response to what has happened should be the same: firmness, political unity and international cooperation. Each and every democrat in the world was on those trains in Madrid. It has been an attack against all of us, against everything we believe in, and against everything we have built.

It is precisely for this reason that we must not send out confusing messages, messages that induce people to believe that we have to make concessions to those demanding that we kneel before bombs. This is not the moment to think about withdrawals of troops. And much less when the terrorists, with their message of death and destruction, have demanded that we surrender. To yield now would set a dangerous precedent that would allow our attackers to believe that they have imposed their conditions on us. It would allow our attackers to believe that they have won.