When President George W. Bush declared a "war on terror" shortly after the attacks of Sept. 11, 2001, the country of Yemen failed to make the short list for the so-called "axis of evil." But U.S. counterterrorism experts say the southernmost country on the Arabian Peninsula has, nonetheless, been closely monitored ever since.
Now, Yemen has been thrust into the media spotlight after reports of active terror plots against Western embassies have forced many to close and intelligence information suggests would-be Christmas Day bomber Umar Abdulmutallab may have been trained and equipped for the attack at an al Qaeda camp inside the country's borders.
"Yemen is a near-perfect haven for terrorists from South Asia," Christopher Boucek of the Carnegie Endowment for International Peace told ABC News. "A year ago, it was hard to talk about Yemen in Washington with everything else [facing the administration]. But it's always had the potential to rise to the top of the list real quick."
Obama administration officials and terrorism experts insist the threat of terrorism emanating from Yemen is nothing new and had been a concern well before the attempted bombing of Northwest Flight 253 Dec. 25. "From the very first day of this administration, we've been focused on Yemen," President Obama's top counterterrorism adviser, John O. Brennan, said on "This Week" Sunday.
Still, the recent flurry of developments in Yemen, including a covert U.S. missile strike on an al Qaeda training camp Dec. 17, represents a sobering reminder of just how difficult the multi-fronted effort to defeat al Qaeda has become, with one expert likening the ongoing struggle to the Cold War.
"When you really remember what people said in 2002 after 9/11, they were all talking about the 'long war,'" said ABC News national security analyst Anthony Cordesman. "Everybody's forgotten that."
"We did this in the case of the Cold War for over half a century and basically we didn't defeat anyone, they collapsed," Cordesman said. "Nothing we can do short of make a combination of efforts at strengthening governments, strengthening economies and direct counterterrorism will make any of these problems likely to be solved in less than a decade, if at any point in the foreseeable future."
Yemen, an unstable country with radical elements, is a case study in the difficulties facing U.S. counterterrorism strategy. Its population of 25 million, with roughly half younger than 15, is the poorest on the Arabian Peninsula. Intelligence estimates suggest there are 200 to 300 al Qaeda operatives living in Yemen.
The country has been home to several successful and attempted attacks against U.S. and Western targets from its soil: Bombers successfully attacked the U.S. Embassy with twin car bombs in 2008 following a failed attempt in June 2001. Al Qaeda operatives also hit the USS Cole docked at the Port of Aden in 2002, killing 17 U.S. sailors.
After 9/11, Yemeni government attempts to clamp down on al Qaeda elements did prove relatively successful and, from 2003 to 2006, there was little al Qaeda violence in the country, Princeton University Yemen expert Gregory Johnsen told ABC News.
But as the terror threats subsided, Johnsen said, so too did U.S. funding to support the Yemeni government. And, by 2007, Yemen had once again become a relative safe haven for al Qaeda and its sympathizers.
The "franchised" nature of al Qaeda, in which extremists anywhere and everywhere can pop up and begin using the name for "branding and convenience, has also made it nearly impossible to pin down and eradicate, analyst Cordesman said.
Although the U.S. State Department has called the Yemeni government an important partner in the campaign against terrorism since 9/11, some experts believe non-government actors within Yemen -- sometimes with government approval -- support al Qaeda, according to a Council for Foreign Relations background paper on Yemen.
Al Qaeda's roots in Yemen date to the Soviet-Afghan War from 1979 to 1989. After Saudi Arabia, Yemen was the second largest source of fighters in the Islamist brigade against the Soviets in Afghanistan. Thousands of Yemenis fought and trained at al Qaeda camps in Afghanistan during that time.
Today, al Qaeda in Yemen has proven resilient, despite continuing and recent attempts by the Yemeni government, with help from the United States, to root it out.
"Al Qaeda has done a very good job at building a durable infrastructure that's been able to withstand the loss of key cell leaders," Princeton' Johnsen told ABC News. "So now, al Qaeda in Yemen is so strong and so entrenched that there really is no easy magic missile solution to the problem."
Top U.S. Gen. David Petraeus met unannounced this weekend with Yemeni president Ali Abdallah Saleh, highlighting just how important -- and delicate -- the country has become in the global fight against terrorism.
U.S. Secretary of State Hillary Clinton said Monday that "instability in Yemen is a threat to regional stability and even global stability" and that the United States is committed to strengthening Yemeni anti-terror efforts.
She also supported British Prime Minister Gordon Brown's calls for an international meeting on Yemen to coincide with the upcoming meeting on Afghanistan in London Jan. 28.
ABC News' Kristina Wong contributed to this report.