When the mechanisms of a country's government -- such as internal security -- do not function, unlawful internal forces and sometimes external elements can operate within that country without the state being able to stop them.

Afghanistan. Iraq. Sudan. Somalia. All four countries are places where central governments became weak or failed, and terrorists moved in. From there, terror has been exported, threatening the world. And as other states become weak, they provide more opportunities for terror to grow.

Islamic Court Militiamen in Somalia patrol the streets of Mogadishu

Former U.S. Defense Department intelligence official Cal Temple, now with the non-governmental Terrorism Research Center in Washington, says there are specific internal conditions that cause a state to become attractive to terrorists.

"Failed states and weak states are fertile ground for terrorism for one primary reason -- a lack of central governance and often [a lack of] political and social participation in these states. These weak institutions, this lack of participation [in governance] and real fragmentation of these societies allows terrorists to come in, take root and plan acts of terrorism."

Why States Fail?

In recent years, the Washington-based publication Foreign Policy has compiled a list of failed states and why they have collapsed. Foreign Policy Senior Editor David Bosco says that along with a breakdown of internal security, there is a set of markers that indicate a country's condition -- including the de-legitimization of its central government, strong factionalization of its ethnic and religious groups, uneven access to and rewards from its economy and the absence of human rights. Bosco says not all states fail for the same reasons, citing two countries in Africa.

"Somalia is one of the classic failed states. Its legitimate government actually controlled one city, and a variety of militias controlled the rest of the country. Sudan, which is not a classic failed state but [is] a state that is in a situation of civil war. So its government doesn't really control its borders," says Bosco.

Foreign Policy's 2006 Failed States Index is topped by Sudan, followed by the Democratic Republic of Congo, while Somalia shares the number six position with another African state, Chad. The Index listed Iraq as number four, while the tenuous security situation in Afghanistan has put it in the tenth position.

Taleban fighters in Afghanistan

The danger of terrorists basing in a failed state and attacking other nations was vividly illustrated by the attacks on New York and Washington on September 11, 2001. The group of people held responsible for those attacks had direct links to Afghanistan and al-Qaida terrorist leader Osama bin Laden, who operated freely in that country after the Islamist Taleban took control after the Soviet Union withdrew its forces in 1989.

While weak or failed states create vacuums that terrorists can exploit, James Dobbins, an expert on Afghanistan with the RAND Corporation research group in Washington, says the Taleban welcomed the terrorists.

"Afghanistan under the Taleban was really a terrorism-supported state. That is to say, you had a relatively weak state dependent, to some significant degree, on financial and other forms of support, from an international terrorist movement -- al-Qaida," says Dobbins.

Cal Temple at the Terrorism Research Center says the U.S. - led incursion into Afghanistan after the September 11 attacks expanded traditional norms on the use of force by one country against another to include suppressing terrorism.

"Diplomacy and economic support is the primary bulwark against failed states and the terrorism they may breed. But if diplomacy and economic support are not enough, then under certain conditions states probably do have the right to go in and help that country root out terrorism," says Temple.

In the case of Iraq, the Bush administration partly justified leading the coalition that toppled dictator Saddam Hussein in 2003 by saying the Iraqi regime had links to al-Qaida and those responsible for the September 11 attacks. But since Saddam Hussein's removal, the absence of sufficient internal security enabled outsiders, such as Jordanian al-Qaida terrorist Abu Musab al-Zarqawi, to move in and conduct terrorist operations. Coalition forces were eventually able to kill al-Zarqawi in a bombing raid this past June.

A New Security Structure

In both Iraq and Afghanistan, the U.S. - led coalitions have engaged in building new security structures to close those countries to terrorists.

Former U.S. intelligence official Paul Pillar, who teaches at Georgetown University in Washington, says it's a task that must be undertaken by everyone.

Iraqi police in Baghdad

"The main thing, if we're talking about other governments [and] the international community, is to provide the kind of support to whatever is trying to be the governmental authority for that territory. And often, things like training, material aid and so on that assist in the development and the increase in capabilities of internal security forces, police forces and so on are a big part of it," says Pillar.

But it takes more than internal security to keep terrorists from exploiting weak and failed states. Those who analyze how terrorism takes hold in such countries say it is critical to build economic systems that give people at all levels a chance for prosperity. Those analysts say that when people have a stake of their own, they are far less likely to embrace extremism.

The September 11th attacks on the United States and other incidents have shown that the international community cannot ignore failed states, especially those harboring terrorists. Most analysts say the international community must be prepared to aggressively assist such countries with a wide range of programs that support development. They add that the fight against terrorism in Afghanistan, Iraq and other nations has shown that the costs will include the lives of some of those who are sent to those troubled countries to help ensure change takes place.

This story was first broadcast on the English news program,VOA News Now. For other Focus reports click here.