Iron discipline that saw the 33 through

They may not take kindly to being called fortunate, given the fear and discomfort they endured during an incarceration that would last almost 70 days, but from the very moment at which they were first trapped underground, the 33 men who have now started to emerge from the San José mine benefited from some crucial strokes of good luck.

The rockfall that trapped them struck at noon on 5 August, when the men were having lunch in a reinforced rescue shelter 700m from the surface. At any other time, during a normal working day, they would have been spread throughout four miles of tunnels, meaning that many of them would have been instantly killed.

When the dust settled, it emerged that the miners had access to a kilometre of what seemed to be stable areas of the mine. That section contained several vehicles, whose batteries they used to power torches. One truck, which had been driven by a former footballer called Franklin Lobos, also contained a small supply of bottled drinking water.

Their next piece of good luck involved the type of mine they worked in. Copper mines (in which gold is produced as a by-product) are inherently safer than coal ones, which emit potentially deadly methane. So although ventilation shafts had been blocked during the accident, the men knew that the only way the remaining oxygen was going to be used up was by them breathing it. In other words, time was on their side.

Thirdly, and perhaps most crucially, the 33 miners had a small quantity of emergency food in the corner of their rescue shelter. They also had leftovers from the lunches they had brought down at the start of their12-hour shift at the small, privately owned facility in the Atacama desert, roughly an hour's drive from the northern city of Copiapo, where most of them lived.

Realising straightaway that the sheer depth at which they were trapped meant it could be days, or even weeks, until they were located by rescuers, the men embarked on a rationing system. They would eat just two teaspoons of canned tuna and a biscuit every 48 hours. Each of these "meals" was to be washed down with two sips of milk.

It was hot in their underground prison, about 30C, but they were able to avoid serious dehydration by supplementing their bottled water by digging a makeshift canal in the floor. By way of a potential last resort, they also drained the radiators of their machinery.

No one yet fully understands the mood in the mine during the ensuing 17 days. A second rockfall, on 7 August, closed off a further hundred yards, presumably adding to the sense of foreboding. There is believed to have been bickering over the rationing system, which some deemed too rigorous. But in subsequent letters, "Los 33" say they've vowed never to publicly discuss any of the tensions that arose.

It seems likely, though, that in the stressful conditions, leaders emerged. One such man was Luis Urzua, a 54-year-old topographer. The eldest son from a large Catholic family without a father, he was a natural authority figure.

Playing to the machismo of his colleagues – tough men in a hard profession – Mr Urzua is believed to have decided that they had a straightforward choice: perish separately, or work together to defy the odds and give themselves the best possible chance of survival. The key to getting themselves out alive, he believed, would be la solidaridad (solidarity).

Mr Urzua, whose colleagues called him Don Lucho, therefore instigated a system under which none of the 33 men could begin eating their tiny meals until all of them had received food. He organised them into three groups, who would venture out, in shifts, to search for signs of any approaching rescue. If nothing else, adding structure to their existence would help to pass the time.

At the surface, meanwhile, a frantic rescue operation was underway. At the behest of Laurence Golborne, Chile's Mining Minister, and a President who had pledged to spend anything it took to get the miners out alive, experts from the state firm Codelco had assumed responsibility for the search. Using maps of the sprawling mine, they drilled several exploratory boreholes, sending listening devices into areas where they believed survivors might be alive.

For two weeks, nothing. Then, on 22 August, came a breakthrough. A probe found its way through a wall just yards from the rescue shelter. It returned to the surface with a note attached to the end. "Estamos bien en el refugio los 33," it read (all 33 of us are well inside the shelter). Those first words had been scrawled in capitals on a scrap of paper by Mario Gomez, the oldest of the miners.

In the first hours after they were discovered, a camera was sent down the borehole. It showed the group peering eagerly out of the darkness, shirtless, unshaven and sweltering, but their eyes blazing with euphoria. Their first request, after food and water, was for toothbrushes.

The rescue teams, meanwhile, swiftly realised that they had two major problems ahead. The first was practical: how to keep the men supplied with sufficient medication, clothing, meals and drinks to keep them alive during a painstaking operation they initially believed might not be over until Christmas. The second was harder to fathom: how to ensure that the men remained psychologically sound during an ordeal that would push any human being to the limit.

A communication system was swiftly designed by Miguel Fortt, a Chilean national and expert in mining rescue operations. He called it "la paloma" (the dove). It consisted of a 3m-long PVC tube, roughly 3in in diameter, which would be lowered via cable to the men, delivering them packages containing whatever could be made to fit inside.

At first, each "dove" took four hours to arrive from the surface, and would contain bare essentials: glucose drinks, together with vitamin and mineral supplements. Later, the system was improved. The PVC was swapped with metal tubes, a further two boreholes were drilled, and journey time improved to 20 minutes. That allowed camp beds, communication equipment and clothing supplies to be sent to make the men's lives more comfortable.

To maintain morale, the rescue team received advice from Nasa, which is used to helping grown men live together in confined spaces for extended periods of time. They encouraged the miners to adopt as many of the trappings of normality as possible, sending down dominoes, books and letters and tape recordings from their families, and widening their diet to include tea, sandwiches, fruit, and later hot meals.

Organised by Mr Urzua, the men were divided into three groups, Grupo Refugio, Grupo Rampa and Grupo 105 – named after the "shelter," the "ramp" and "Level 105", which are sections of the mine where they slept. They then established a working shift pattern. When off duty, they slept, exercised (by running or using rubber exercise bands) and sent video, audio, and written messages to their families. Lights shone from 7.30am until 10pm, mimicking daylight. To keep all the trappings of a normal workplace, Mr Urzua used the bonnet of a mine vehicle as his desk, and sent up maps of the area.

Mr Urzua wrote each of the men an official job description. Some became "palomistas," unloading the regular supply of "doves". Others would patrol the mine to check on the structural integrity of its walls. Jimmy Sanchez, the youngest of the group, was the "environmental assistant", who monitored conditions underground with a handheld computer that measured oxygen, CO2 levels and air temperature.

Other aspects of daily life soon began to fall into place. They would shower each morning under a natural waterfall 300m up the tunnel, using supplies of shampoo to clean off the orange-coloured mud that found its way almost everywhere. The more religious men – at least two of them "found God" during their ordeal – would take part in a daily prayer organised by Jose Henriquez. Others would listen to uplifting poems written by Victor Zamora, the group's in-house poet.

It was, of course, very far from plain sailing. Many developed fungal skin infections, and almost all will now require extensive dental treatment. Medical teams at the surface also repeatedly found themselves clashing with some of the miners, whose natural machismo led them to consider the mandatory daily conversations with psychologists to be un-necessary, and perhaps undignified.

They also took exception to the rescue team's refusal to send supplies of wine and cigarettes down to them, to prevent depression and keep the atmosphere as unpolluted as possible. They also objected to the decision to censor letters from relatives to the men that were thought to be insufficiently optimistic in tone.

At one point, in mid-September, some of the miners effectively went on strike, refusing to speak to their medical handlers. As a result, the psychologists withdrew TV and music that was being provided via the communication system. When the men agreed to speak with them again, a delivery of cigarettes arrived in a "dove". This carrot-and-stick approach was described by one medic as "like an arm-wrestle".

But by that stage, three drills – Plan A, Plan B, and Plan C – were cutting through the rock to reach the cavern. By early October, they knew breakthrough was imminent. And on Saturday, the Plan B drill broke through. After two months underground, the final stage of their journey to freedom could at last begin.

Follow Guy Adams on Twitter: @guyadams