(CNN) -- Imagine the entire population of Kentucky forced out of their homes in the past 25 years, with many of the residents moving to a neighboring country.



Displaced children at a camp in El Barrancon, Colombia, earlier this year.



That's what has happened in Colombia, a country of 45 million where up to 4 million people -- roughly the population of Kentucky -- have been forced to flee fighting between government forces and an entrenched Marxist rebel group. So many Colombians have taken flight to escape violence that the nation has the second largest number of internally displaced people in the world -- surpassed only by Sudan in Africa.



Oftentimes, the violence is not incidental.



"Violence against civilians is a strategy of war for all the parties involved in the warfare," said Ellen Beattie, who worked for relief agencies in Colombia for 15 years. "That's the problem. They do it on purpose. They use it as a strategy. Vicious."



Exact figures are hard to come by.



Reliefweb, a United Nations Web site that provides information to humanitarian relief organizations, says nearly 400,000 Colombians were displaced last year. The Colombian government puts the number of displaced at 255,000 for 2008.



Likewise, the Colombian government says nearly 3 million citizens have been displaced inside the country in the past few decades. But the non-governmental Consultancy for Human Rights and Displacements, known in Colombia as CODHES, estimates more than 4 million people have had to leave their homes since the 1980s.



Mauricio de Vengoechea, a political analyst with the Newlink Group consulting firm, says about 200,000 Colombians have ended up in Ecuador, which has granted 5,500 residency permits in the past eight weeks.



At the heart of the violence lies a guerrilla war with the Colombian government and paramilitary groups on one side and the FARC, which is the Spanish acronym for Revolutionary Armed Forces of Colombia, on the other. The FARC has been waging war against the government since the 1960s and has major strongholds in the jungles of southwest Colombia, near the 366-mile (590-kilometer) border with Ecuador.



Narcotraffickers also have strongholds in the area and are often allied with the FARC, who provide security and intelligence. Many times the rebels and the narcotraffickers are one and the same. The guerrillas use drug money to buy weapons.



"There are large parts of Colombia where the state has no presence, no police, no army, nothing," said Myles Frechette, the U.S. ambassador to Colombia from 1994 to 1997. "That's where the narcotraffickers hang out."



That makes it valuable territory for the guerrillas and narcos, said Beattie, executive director of the International Rescue Committee office in Atlanta, Georgia.



"They're more willing to fight over land that is strategic," she said. "You've poured gasoline on the fire with that."



As the army, paramilitaries and the guerrillas fight for territory -- often retaking land one side or the other had held before -- the civilian population gets caught in the middle. When one side comes in, Beattie said, everyone living in the area is suspected of having collaborated with the enemy. That sometimes leads to massacres, or at least kidnappings and death threats.



"The majority of displacements in Colombia are not because of combat, but because people are directly threatened," said Gustavo Valdivieso, spokesman in Colombia for the United Nations High Commissioner for Refugees. "They are told, 'Leave or be killed.'"



Many times, indigenous populations in far-flung places suffer the most.



That's what happened earlier this year to the Awa tribe in southwest Colombia. The FARC admitted in an Internet statement that guerrillas "executed" eight people February 6 in the town of Rio Bravo because the rebels believed the Indians were gathering information to give to the Colombian military.



The Human Rights Watch organization said the guerrillas tortured some of the Awa before killing them with knives.



Luis Evelis Andrade of the National Indigenous Organization of Colombia said the FARC had targeted the Awa because the Indians don't want to get involved in the armed struggle and refuse to reveal
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