Hunger striking Guantanamo prisoners who are force-fed a liquid nutritional supplement undergo a brutal and dehumanising medical procedure that requires them to wear masks over their mouths while they sit shackled in a restraint chair for as long as two hours. The prisoners remain this way, with a 61cm - or longer - tube snaked through their nostril until a chest X-ray, or a test dose of water, confirms it has reached their stomach.
At the end of the feeding, the prisoner placed into a "dry cell" with no running water. A guard then observes the detainee for 45-60 minutes "for any indications of vomiting or attempts to induce vomiting". If the prisoner vomits he is returned to the restraint chair.
Force-feeding is a violation of the Geneva Conventions because it's cruel and dehumanising.