For the hunger strikers, breakfast at Guantanamo begins with a visit from the emergency reaction force: five military police officers in riot gear, trained in the "forced cell extraction" of prisoners.

Since the protest began, the majority of the 166 men held at the camp have been placed on "discipline" for breaching regulations. Twice a day those that refuse to comply are shackled, slammed to the floor and dragged out to be fed.

Details of what follows - the military describes it as "enteral feeding" - can be gleaned from the camp's standard operating procedure (SOP) manual. The prisoner is strapped to a chair with a mask over his mouth. Medical personnel insert a tube 3mm in diameter up his nostril, push it down into his stomach and pump in a nutritional shake called Ensure, sometimes mixed with an anti-nausea drug called Reglan. This takes around 30 minutes, after which the prisoner is transferred to a "dry cell" for two hours, under observation, to ensure that he does not vomit up the food.

In testimony provided to the Sunday Herald by defence lawyers, prisoners describe the feedings in grim detail.

"The process of being force-fed hurts a great deal, particularly because I had surgery in my nose so my nerves there are very sensitive," said Ahmed Belbacha, an Algerian who has been held without charge at Guantanamo since March 2002.

"Sometimes they botch putting the tube in and tears stream down my cheek. I asked for a size eight tube, and they refused, saying 'You don't like size 10? Eat!'"

"The chair reminds me of an execution chair. It's a very painful experience," said Nabil Hadjarab, another Algerian inmate. "I'm suffering every day. In a way this isn't new - I've been suffering for over 11 years - but the experience in the chair is something different."

Both were cleared for release long ago, but have no idea when or whether their detention will end. The recent news that the US government is ready to send two unnamed prisoners back to Algeria now that "security conditions" there have been met - there are five Algerians cleared for transfer at Guantanamo - provided a glimmer of hope, but no more.

No-one outside the camp knows for certain how many prisoners are participating in the strike. The official figure is currently 81 men, of whom 45 are being force fed. Shaker Aamer, the one remaining British inmate, estimates that 126 men are taking part, adding that only the elderly and sick have opted out.

Defence attorney Carlos Warner has speculated that a different group of 45 men is being force-fed each day, to obscure the size of the protest. The list of strikers is classified, but under SOP regulations, prisoners must be force fed when they refuse nine consecutive meals or their body weight drops below 85% of the normal range for their height.

"A lot of people are really in trouble now, the strike has gone on so long," Aamer said. "Some people are just skin and bones. It's not like the hunger strikes in 2005 any more. We've been through so much that the damage to our minds and bodies will be worse."

The strike began on February 6, following an aggressive shakedown of the cells in which Korans were searched - a grave violation of Muslim principles. There is an element of chicken and egg to this: did the prisoners strike in response to a tough new regime at the camp, or did the new commander, Colonel John Bogdan, introduce most of the harsh disciplinary measures in response to the strike?

Whatever the answer, detainees who were previously free to mingle are now kept in solitary confinement for 22 hours a day.

Anything that the military deems to be a comfort item has been stripped from the cells, including the yoga mats prisoners use as mattresses, their pillows, photographs and letters from family members. If a prisoner covers the cell camera when using the toilet, the emergency reaction force is called. In order to talk to their lawyers by telephone, inmates must submit to two body cavity searches.

"These are clearly punitive measures designed to break people's will," said Cori Crider, a lawyer from the British charity Reprieve who represents several Guantanamo detainees.

Warner, a public defence attorney in Ohio with 12 clients at Guantanamo, agreed: "The military at this point thinks they can break it by isolating individuals, force-feeding them, hoping it goes to the background," he said. "We have never trusted the military's numbers. The strike will only end when people start being released.

The holy month of Ramadan, which ended on August 7, presented a particular set of problems.

"We understand that observing the daytime fast and taking nothing by mouth or vein is an essential component of Muslim observance of Ramadan," Guantanamo spokesperson Captain Robert Durand told the Miami Herald. "And for those detainees on hunger strike we will ensure that our preservation of life through enteral feeding does not violate the tenets of their faith."

There was a get-out clause - "unforeseen emergency or operational issues" - but apparently Durand's promise was kept. Each night, between sunrise and sunset, at least 45 men broke their fast strapped to a chair, with a tube forcibly inserted up their nose, their bodies and dignity violated but their religious faith respected to the letter.

"I'm still being force fed, once a night, and the way that they do it in Ramadan makes us all exhausted," Belbacha told his lawyers. "There are two waves: the first group goes at eight o'clock, and the second group later - in theory, it's at 10pm, but sometimes it happens at midnight or even later. It's extremely tiring."

Prisoners were threatened with an entire month in solitary, without breaks, for refusal to comply, a particularly harsh punishment during Ramadan, when communal prayers assume added importance.

Contrast this with Ramadan last year and it is clear how badly conditions have deteriorated. Then, guards handed out breakfast boxes of milk, yoghurt, cereal, eggs, bread, peanut butter and jam before dawn. Prisoners ate, prayed, washed clothes, exercised and watched television together.

"You would have heard the military boast, even six months ago, about how delightful this facility was," said Crider. "That facade is starting to crumble."

Durand said most detainees ate lamb to break their fast on the first day of Ramadan, a claim greeted with scepticism by defence lawyers.

Clive Stafford-Smith, from Reprieve, accused the military of "cheating on the numbers as usual" by counting this religious gesture as a meal. And while there was definitely a softening of the protest during the holy month, prisoners have told their lawyers it was temporary.

"The numbers will rise again," said Warner. "I have no sense that the men's spirit has been broken or that the strike is waning."

Doctors' groups including the American Medical Association and the British Medical Association have written to the US government, asserting the right of prisoners to refuse food.

The World Medical Assembly guidelines on hunger strikes are unequivocal: "Forcible feeding is never ethically acceptable. Even if intended to benefit, feeding accompanied by threats, coercion, force or use of physical restraints is a form of inhuman and degrading treatment."

In June, an extra 37 medical staff were flown in to deal with the hunger strike, bringing the total of doctors and nurses on base to around 140.

Dr Steven Miles, a professor at the University of Minnesota and an expert on medical ethics, has been one of the most prominent critics. He said a nurse who objected to the force feedings on grounds of conscience would be sent home from Guantanamo and replaced.

"That's important, because the physicians are working on behalf of the interrogation and detention centre, rather than working on behalf of the prisoners," he said.

That is in violation of the basic ethical principle that a doctor's primary obligation is to the patient.

The camp's senior medical officer, who cannot be identified for security reasons, said that "if a patient is threatening to hurt themselves or kill themselves we're not going to stand by and watch that happen" - in short, prisoners are being force-fed for their own good.

A Pentagon spokesperson, Lieutenant Colonel Todd Breasseale, said that "choosing to sit by while [a detainee] starves himself to the point of endangering his life is … the worst kind of victor's justice: repugnant and wholly unacceptable".

The policy's unspoken rationale is that another death at Guantanamo would focus the world's attention on a prison camp that President Obama vowed to close as soon as he took office. It remains stubbornly open more than four years later, even though more than half the inmates have been cleared to go home.

On May 23, in his much-heralded national security speech, Obama noted that the prison "has become a symbol around the world for an America that flouts the rule of law" and again expressed his determination to shut it down.

"Look at the current situation, where we are force-feeding detainees who are holding a hunger strike," he said. "Is that who we are? Is that something that our founders foresaw? Is that the America we want to leave to our children? Our sense of justice is stronger than that."

He announced that the ban on transfers from Guantanamo to Yemen would be lifted and once more blamed Congress for frustrating attempts to reduce the number of prisoners held at the camp.

Warner's assessment of this claim was blunt: "That's a complete falsehood and the law says it. He has the power to transfer individuals unilaterally if it's in the interests of national security.

"He likes to blame Congress, which is an easy way for him to get out of his own noose, but the bottom line is that he has the ability to transfer individuals right now."

In May, Senator Carl Levin, chairman of the Senate committee on armed services, wrote an open letter to the president asking why he has not used the national security waiver to transfer inmates who have been cleared for release. Rehabilitation centres designed specifically for Guantanamo inmates have been built in Kuwait and Saudi Arabia, under US supervision. The Yemeni government has demanded repatriation of its detainees.

"For a long time it was about whether Obama had the authority," said Warner. "Now it's about whether he has the political courage."

The hunger strikers are ready to die, if their captors will let them. At his last meeting with Cori Crider, Nabil Hadjarab was so weak that he could not hold his head up for long.

"I do not want to die, but I am prepared to," he told her.

"For years I never thought about being on hunger strike, but I am doing this because I want to know my destiny. I cannot abide not knowing anymore.

"The most important thing in my life is my health, my body. But what good are these things without freedom?"