On Sunday, a complex operation began in Chiang Rai, Thailand, to rescue the 12 boys, aged 11-16, and their 25-year-old soccer coach, who are trapped inside a flooded cave.

On Tuesday night, that mission came to an end, as they were all brought to safety. The soccer team have been stuck for 17 days.

Just INCREDIBLE.

ALL of the boys and their coach have been rescued from the Tham Luang cave in Thailand.

LATEST: https://t.co/8xSugaOyB6 pic.twitter.com/MPr6Sdy8NZ

— 3AW Melbourne (@3AW693) July 10, 2018

ABC reported that the rescue trip with each boy was expected to take eight hours, and was an incredibly delicate operation. On their way out, the boys needed to dive and wade through muddy waters, which, in some parts, had almost no visibility.

Australian doctor Richard Harris will be one of the last to evacuate, and Sydney Morning Herald reports he has swum all the way to the trapped boys for three days in a row now, to complete a medical check for each boy ensuring they were fit for the exit journey.

According to ABC‘s South-East Asia correspondent Liam Cochrane, the narrowest gap in the journey was just 38cm in diameter – only slightly bigger than the width of a school ruler. At this point, the boys had to be pushed through the gap, which was only large enough to fit their head through.

“The man who is leading this rescue operation described them as having the boys underneath them and swimming below and guiding them through the waters with almost no visibility,” said Cochrane.

But how did a group of teenage boys and their soccer coach venture so far into a cave that they now need an international operation to rescue them? Why were they there, and how did they become trapped?

On June 23, the head coach of the Moo Pa (Wild Boars) soccer team, Nopparat Khanthavong, had an appointment, so left his 25-year-old assistant, Ekapol Chanthawong, in charge of the team. In a Facebook message shared with The Washington Post, the coach instructed Ekapol, "Make sure you ride your bicycle behind them when you are traveling around, so you can keep a lookout."

But when the coach checked his phone at 7pm, there were at least 20 missed calls from worried parents, whose sons hadn't returned home.

He called Ekapol, as well as many other members of the team, and only one 13-year-old answered. The boy told Nopparat that the team had gone exploring in the Tham Luang caves. Nopparat went there immediately - to discover bikes and bags at the entrance to the cave, and water seeping out.

Speaking to The Washington Post, the 37-year-old said, "I screamed — ‘Ek! Ek! Ek!’ My body went completely cold."

It's believed the team and their coach ventured into the cave for an 'initiation ceremony' which involved writing their names on the cave walls. After the group entered, however, it started to rain, sending floodwater into the mouth of the cave. The monsoon flooding blocked the group's exit route, so they kept walking until they found a space that was slightly elevated and dry. This is where they remain stuck.

A large-scale search and rescue operation was launched, involving specialists from Australia, China, Japan, the UK and the US, while persistent rain made it exceedingly difficult to find the group. On July 2, two divers found them alive, about four kilometres from the cave's entrance.

In the days since, a doctor and a nurse from the Royal Thai Navy have remained with the group, giving them food, water and medical support.

The national coordinator of the National Cave Rescue Mission, Anmar Mirza, who has been involved in cave rescues for 30 years, emphasised the complexity of the rescue operation in an interview with CBS. 

"This is the most scary situation that a person could go through," he said. "You can't make a horror movie that would even compare."

"The trust factor between the children and diver makes it - it's probably 90 percent of what gets them out of the cave," he said.

According to rescuers, Ekapol was among the weakest in the group, because he gave his food and water to the boys in the days before they were found.

The risks associated with the rescue mission were underscored by the death of 38-year-old former Navy SEAL Saman Kunan on Thursday, who died underwater after bringing oxygen tanks to the boys.

The fact that all 12 boys and their coach have been brought to safety is a truly remarkable feat, and a testament to the indomitable nature of the human spirit. But it's likely that for those who were trapped for 17 days, not knowing whether they'd ever escape, the physical and psychological trauma is far from over.