"In some cases, detainees under our control for as long as two years, who had resisted talking to us and refused to communicate any relevant information, have over the last six months elected to begin to talk with us about where they were and what their activities were," Brigadier-General Jay Hood told the House Armed Services Committee on Wednesday.
He is commander of the joint task force overseeing operations at Guantanamo.
The Pentagon often says that useful information in the fight against "terrorism" continues to be gleaned from the 520 detainees held at the prison on the US military base even though most of those held have not been on the battlefield in several years.
Military officials have been trying to prove the prison remains relevant in the face of increasing calls for it to close.
Hood said information from detainees at Guantanamo has helped the US locate and identify terrorist networks as well as understand how terrorist cells communicate, finance and train recruits.