From car bombings that killed scores to ritualized executions meant to build fear one victim at a time, it was Iraq that bore the brunt of terror in 2004 - with insurgents targeting Americans, other foreigners and Iraqis working to rebuild the country.
But Europe learned it was not immune in March, when explosions on commuter trains in the Spanish capital of Madrid killed 191 people. In videotapes, Muslim militants said they acted on behalf of al Qaeda in revenge for Spain's alliance with the United States in Iraq and Afghanistan.
Three days after the attack, Socialists who had pledged to pull Spanish troops out of Iraq ousted former Prime Minister Jose Maria Aznar's conservatives. The Socialists quickly made good on their withdrawal promise, leading some to declare al Qaeda had pulled off a political victory.
An October terrorist kidnapping in Iraq also appeared aimed at voters in a European ally of the United States. Videotapes showed British hostage Kenneth Bigley pleading for help from British Prime Minister Tony Blair as Britain prepared for elections expected in 2005. In the end, Bigley, 62, was beheaded, as had been two Americans abducted with him: Jack Hensley, 48, of Marietta, Ga., and Eugene "Jack" Armstrong, 52, of Hillsdale, Mich.
On Dec. 6, both Americans and Saudis were reminded of how tough it is to stop terrorism as five gunmen - four of them Saudis - attacked the U.S. consulate in Jiddah, Saudi Arabia. Five consulate employees - all from the Middle East or Asia - were killed and 10 people, including two Americans, were wounded. Four of the attackers were killed and the fifth captured as Saudi forces retook the building.
Jonathan Stevenson, a Washington-based counterterrorism expert with London's International Institute for Strategic Studies, notes the al Qaeda terror network and its sympathizers sought softer, U.S.-linked targets around the world since security has been tightened inside the United States and al Qaeda has been left without a base to operate from in Afghanistan.
But ultimately, Osama bin Laden's movement hopes to pull off another spectacular strike in the United States, Stevenson said. They have "reserved the United States for the highest value, most iconic attacks," Stevenson said.
Bin Laden may be able to do little more than issue videotaped threats from his hiding place, but his allies are encouraged by each appearance, like one in November in which he for the first time he clearly claimed responsibility for the Sept. 11, 2001 attacks and said the United States must stop threatening Muslims if it wanted to avoid "another Manhattan."
While al Qaeda regroups, the U.S. invasion of Iraq provides an arena for Muslim extremists from around the world bent on fighting Americans. While foreign "holy warriors" are a minority among Iraqis fighting for nationalist reasons, the outsiders wield influence greater than their numbers.
The most prominent is a Jordanian high school dropout known as Abu-Musab al-Zarqawi, who confirmed what many had long suspected when he posted a Web pledge of loyalty to bin Laden in October.
Al-Zarqawi is said to have beheaded at least two kidnapped American civilians himself - Nicholas Berg and Eugene Armstrong. His group has claimed responsibility for numerous attacks on civilians and coalition and Iraqi forces.
His goal is to make Iraq ungovernable, robbing the United States of a chance to show it is serious about pledges to bring democracy and stability to the heart of the Arab world. Iraq's neighbors had opposed the U.S. invasion from the start. They now fear that young men from their countries who went to Iraq will come home battle-hardened, even more radical in their beliefs, and determined to overthrow regimes in places like Saudi Arabia - which suffered several terror attacks in 2004, notably the U.S. consulate attack.
The sooner U.S. troops leave Iraq, the sooner that threat to the neighbors will subside. But as 2004 ended, the United States announced plans to increase its troops in Iraq to an all-time high of about 150,000 by mid-January, hoping to bolster security before national elections scheduled for Jan. 30.
It was unclear when Iraq would be deemed calm enough for the Americans to leave. Anthony Joes, a guerrilla warfare expert at St. Joseph's University in Philadelphia, said history shows that despite the weapons and manpower the United States wields, it faces an enormous challenge.
"Iraq is 29 times as big as Chechnya, where the Russians have been declaring `final victory' for the past 10 years," Joes said. "Iraq is 32 times the size of Northern Ireland, where for a quarter of a century after 1972 a few hundred criminals tied up 22,000 British troops."
On the Internet sites where extremists share anger and ideas, the U.S. invasion is portrayed as proof bin Laden is right in arguing the United States wants to control Muslim land and humiliate Muslims. Iraqi civilians caught in the crossfire are portrayed as victims of American brutality. Iraqi leaders cooperating with the United States in hopes of building a democracy are portrayed as traitors to Islam.
"Now any radical young Muslim sees this expression of American power in the heart of the Middle East, puts two and two together and makes 12," said Peter Lawler, a professor of international relations at Manchester University.
That radical young Muslim could live in Karbala or Amsterdam.
On Nov. 2, Dutch filmmaker Theo van Gogh, who had produced a television drama critical of how women are treated in some Muslim societies, was murdered in the Dutch capital. His throat was slit and he was found with a note secured into his chest with a knife threatening holy war against the Netherlands' "infidel" government.
Authorities arrested an alleged Islamic extremist who holds Dutch and Moroccan citizenship, fueling right-wing calls to halt Muslim immigration to Europe, but also soul-searching about how better to integrate Muslims into Western societies.
Lawler said young Muslims in Europe and elsewhere are angered by what they see as America's bias toward Israel and its support of Arab dictatorships. If their anger can be assuaged by assurances the West will work for democracy in the Middle East, extremists will find it harder to recruit suicide bombers.
"That involves long-term, creative, subtle diplomacy," he said.
Fitting, as the terrorists portray their campaign as rooted in history and likely to be waged for generations to come.
By Donna Bryson