West dodged several bullets in a relatively terrorism-free 2006

MADRID, Spain -- Bombs left on commuter trains in a busy station in Germany. A plot to blow up tunnels and flood New York City's financial district. Another to bring down packed commuter airliners flying out of London.

Islamic militants had no shortage of murderous ideas in 2006, but for the first time since before the Sept. 11, 2001, attacks, a year neared its close without a major attack in the West.

In a wide-ranging analysis, security and intelligence leaders around the world said that their success was due to more than just luck. Far greater human and technological resources, tougher anti-terror laws, a deeper understanding of the homegrown nature of the threat and the hard lessons learned from past failures -- all these have all helped avert catastrophe, they said.

But they also cautioned against complacency, saying another attack is inevitable. A senior Spanish intelligence official who recently stepped down as head of a national counter-terror unit warned that the absence of deadly attacks this year does not mean the world should expect similar results in 2007.

Reinforcing the reality that high-casualty terrorism is still a threat, not only in the West, a bomb attack on trains in Mumbai, India, in July killed more than 200 people. India suspects Islamic organizations both at home and in neighboring Pakistan of being behind the bombings.

On Dec. 10, John Reid, Britain's top law enforcement official, said an attack during the Christmas and New Year holiday was "highly likely," and the security and intelligence officials, who were interviewed before the holiday, echoed that warning.

Anger among many Muslims is still high over the war in Iraq, the publication of cartoons of the Prophet Muhammad, Israel's war against Hezbollah militants in Lebanon and remarks by Pope Benedict XVI that many Muslims considered insulting.

Magnus Ranstorp, a terrorism expert at the Swedish National Defense College, said the absence of attacks on European soil in 2006 reflects a better understanding of how the terror networks operate -- and a little bit of luck.

Analysts and intelligence officials say the nature of the threat has changed dramatically since Sept. 11, 2001, with concern largely focused on homegrown groups driven by local grievances, rather than professional terrorists trained by al-Qaida and with direct links to Osama bin Laden.

While these groups have the advantage of being small, they are often less sophisticated and easier to catch. Thousands of suspected radicals are under surveillance across Europe, making it harder for plots to emerge.

The closest call in 2006 may have come in Cologne, Germany, when two crude bombs on trains failed to detonate. The biggest threat was the London airliner plot. Lesser defined schemes against the Jewish Quarter in Prague, a church in Bologna, Italy, and the Milan subway also failed.

In the United States and Canada, authorities uncovered plots -- some seemingly little more than fantasies -- to blow up the Sears Tower in Chicago, flood lower Manhattan by blowing up tunnels under the Hudson River, and attack public buildings in Ontario.

Authorities in Morocco arrested at least 56 people, among them soldiers, police and the wives of Royal Air Maroc pilots, over an alleged plot to blow up foreign targets. Indonesia, one of the countries most frequently hit by Islamic radicals, enjoyed its first attack-free year since 1999.

"Security has certainly improved," said Paul Wilkinson, chairman of the Center for the Study of Terrorism and Political Violence at the University of St. Andrews, Scotland. "We are seeing incremental improvements in intelligence and better international cooperation which has continued despite disagreements about Iraq. The sharing of intelligence has been extremely important."

But he warned that the overall threat has not decreased, and those on the front lines agree.

"Any assessment that the threat of terrorism has almost ended is a hallucination," said Rodolfo Mendoza, a senior Philippine police official who has led a manhunt for al-Qaida militants in his country in the past and done extensive studies on terrorism. "The silence now is not a guarantee that they will not strike again."