Twice a day at the military detention center at Guantanamo Bay, Cuba, guards take a group of detainees from their cells, one at a time, to a camp clinic or a private room on their block.

The detainees are offered a hot meal or a liquid nutritional supplement and, if they refuse, they are strapped into a chair. A nurse then passes a tube through their noses and down into their stomachs; for one to two hours, they are fed a drip of Ensure while a Navy corpsman watches.

Those who have experienced force-feeding have described it as painful. But, as the prisoners at Guantanamo Bay are well aware, fasting and then enduring the procedure can also bring political advantage.

From British-run prisons in Ireland to detention facilities in Israel, the hunger strike has long been a political weapon wielded by the imprisoned or the powerless. With their protest, the 100 men refusing food at Guantanamo Bay — 23 of whom are being fed via nasogastric tube — have pushed the largely forgotten issue of their indefinite detention back on to Washington’s agenda.