“Riverine” operations and the U.S. military have a dark history in Colombia. One of the worst atrocities in the last decade of the Colombian civil war was the infamous Mapiripán massacre of 1997. For five days a force of 100 paramilitary fighters, coordinating with high-ranking officers in the Colombian military, terrorized the town of Mapiripán on the banks of the Guaviare river. (The river separates the departments of Guaviare and Meta and lies in one of the most important coca-producing areas of the country.) The paramilitaries systematically killed at least 30 townspeople over the course of 5 days. Carlos Castaño, the founder of the United Self-Defense Forces of Colombia, organized the operation and was present; he later admitted that he and his men killed 49 people. Some claim the death toll was even higher; many of the bodies were dumped into the Guaviare River and never found.

According to Ignacio “Nacho” Gómez’ celebrated investigative report on the incident published in the Colombian newspaper El Espectador in 2000, the surrounding area was crawling with U.S. military personnel at the time. The gringos were busy with an intensive program training the same Colombian military officers involved in planning the massacre in “river combat” techniques.  While only the U.S. soldiers’ Colombian students have been directly implicated, many believe U.S. Green Berets were on the river while the paramilitary boats were besieging the town and were aware of what was happening.

Gómez began receiving death threats after looking into these events and was eventually forced to leave the country for several years.

From his article in El Espectador:

For eight months starting in May 1997 the Green Berets' center of operations was the Army Special Forces School, five minutes away by boat or car from the Counternarcotics Base at San José del Guaviare and "headquarters" for the State Department programs for the eradication of coca plantations. The name of the locale is Barrancón; it is an island formed around a rock in the bed of the Guaviare River; from its heights the river and the Sabanas de la Fuga, a historic "sanctuary" for the Farc, can be seen.

When Senator Leahy requested information on those activities, Solic's director, Brian Sheridan, explained that the course that began on May 14 in Barrancón dealt with "mission planning and military decision making" and other specific matters related to "light infantry."

Colombian reports indicate that the unit being trained was commanded by Colonel Lino Sánchez. The Counternarcotics Police Intelligence Office gave the State Department and the federal prosecutor's office a report according to which, in those days, Sánchez pioneered a plan to introduce paramilitary forces in the sprayed areas, within the framework of U.S. programs and announced that some aid had arrived that would enable him to "teach the guerrillas a lesson."

The federal prosecutor's office discovered that on July 12, 1997, a group of fifteen men personally chosen by Carlos Castaño Gil, flew in two planes from Urabá to San José del Guaviare Airport, which is shared by the Counternarcotics Police and the garrison in which Sánchez had his office. On the Barrancón road, Castaño's group joined the paramilitary forces of Casanare and Meta, and from there they went by truck to Charras, on the opposite bank of the Guaviare River, across from Mapiripán.

The boats on which they all crossed the river encounter no problem when they passed the Marine Infantry post in Barrancón, built by the Americans and in which "river combat" training took place. The paramilitary forces, more than 100 men, remained in Mapiripán from July 15 to 20, and were at no point challenged either by civilian or military authorities.

These dates coincide with three Special Forces deployment dates mentioned in the report to the U.S. Congress, but none of those listed by Sheridan occurred during the massacre days. However, the federal prosecutor's office and other officials say they crossed paths with U.S. military in San José, when they traveled to Mapiripán to aid the massacre survivors and open their investigation.

Government files include five reports from five military commands, including General Bonett's, mentioning the maneuvers that took place at that time in Barrancón to celebrate the closing of a "special forces course".

But they only indicate the presence as guest of honor of General José María Balza, Commander of the Argentinian Military Forces.