He was watching it live on TV with his mates at a house in Wamberal on the Central Coast.

The TV didn't have a remote control.

The channel had to be changed manually.

As they watched pictures of the first World Trade Centre building on fire, they soon grasped the enormity of the situation.

"Someone changed the channel and the next thing you know it's on that channel, too. It was on every channel," said Mr Thomlinson, who is now 40 and lives at Forresters Beach on the Central Coast.

"Everyone was in shock. Then we saw the second tower get hit. You kind of knew everything was going to change that day."

It soon became clear that the terrorist organisation al-Qaeda, led by Osama bin Laden, was behind the attacks. Four commercial airliners had been hijacked by 19 terrorists.

The third plane was flown into the Pentagon, while the fourth crashed in a field in Pennsylvania, after a struggle between passengers and hijackers. Its target was the White House or the US Capitol Building.

US president George W. Bush first mentioned the "war on terrorism" five days later. It became the "War on Terror" in a speech to Congress soon after.

"Our enemy is a radical network of terrorists and every government that supports them," President Bush said at the time.

On September 20, nine days after the attacks, President Bush demanded that the Taliban government of Afghanistan turn over bin Laden and al-Qaeda leaders or face attack.

The following month, US forces and their coalition allies invaded Afghanistan.

Mr Thomlinson joined the military in January 2005. He became a commando in the Australian special forces.

He said the September 11 attacks and War in Afghanistan may have subconsciously influenced him to join the military.

"There was a lot of coverage of military things and a lot of TV shows and movies with military themes," he said.

Joining the military "wasn't on my to-do list", but he was finding it hard to "get ahead and be rewarded for hard work" on the Central Coast.

"I'd found too many situations where I worked really hard for someone and the other guy got promoted," he said.

He started to think the military would be a place where he could "test whether I'm good enough".

"I remember that's what I was thinking when I went through the Army website. I remember my grandad's picture. I used that as inspiration. His picture used to be next to Mum's computer, which was what I was using to find the path that I should take," he said.

His grandad Fred fought in World War II in the Pacific.

"He served in WWII for five years. He was injured from a shrapnel wound in New Guinea on his last deployment," Mr Thomlinson said, recalling him marching on Anzac Day.

"He died when I was eight. I wanted to carry that legacy on. I wanted to make the family proud.

"It was definitely a contributing factor that there was international conflict. I knew that by joining, it would give me the opportunity to make a difference and test myself in the most extreme way possible."

Being a commando involved keeping cool under pressure and "critical thinking when you're exhausted and under extreme duress".

"I really liked that. I liked the test," he said.

During commando training, he would tell himself: "How bad do you want it? Do you want to be that guy?"

Through the arduous training required to be an elite soldier, the thought that it would one day be used in a real conflict made it worthwhile.

"It was good to know the training was going somewhere," he said.

Mr Thomlinson deployed to Afghanistan in 2009.

Six weeks into his mission, he was on night patrol with two other commandos when their special reconnaissance vehicle drove over an improvised Taliban bomb.

His injuries resulted in both his legs being amputated. The medical team thought it was a miracle he survived. His fellow commandos had burst ear drums and minor scratches.

With US President Joe Biden withdrawing troops from Afghanistan and the 20-year anniversary of the 9-11 attacks falling on Saturday, Mr Thomlinson reflected on the War on Terror "in a really positive way".

"I'm really proud of everyone who I served with. I've seen firsthand the sacrifices made," he said.

"I'm really proud I can call myself one of those people and say I served with pride in the ADF [Australian Defence Force]."

He considered Afghanistan a successful operation because "we haven't had another 9-11".

"We caught and killed bin Laden then finished off the rest of the upper leadership.

"It was unfortunate for the people of Afghanistan that it was in their country. I feel for them. I don't think anyone should have to grow up in a war-torn place. It's just horrible."

He said the terrorists had to be stopped.

"They needed a message that things like that [the 9-11 attacks] weren't going to stand," he said.

"It's not something you can get away with in a free world."

He said there was a lot of "finger-pointing" around the Afghanistan withdrawal.

"I don't look at it in that way. The exit from Afghanistan was a five-year wind down. They knew the date they were leaving," he said.

"We did a great job equipping a country that was really struggling at the time. We equipped the defence force, we trained them, we put so much effort into making sure that they had every fighting chance.

"That's one of the reasons I'm so proud to have served. It's an Australian thing to give people a fighting chance at success. We did everything we could when it came to that."

Nowadays, his main focus is his wife and two young children. He's also a keen golfer.

"I'm grateful to the Magenta Shores Golf Club [just north of The Entrance]. They've been phenomenal to me for 10 years.

"They've deeply understood how much I need sport as an outlet for my mental wellbeing. I need something to continually work on."

Once he realised he could play golf well with a specific type of prosthetic, he went for it.

"I'm a world-ranked disabled golfer, which is cool."

He studied acting and appeared in the 2016 Hollywood blockbuster Hacksaw Ridge, directed by Mel Gibson. In 2018, he appeared on Australian Survivor. He's met the likes of Angelina Jolie, Brad Pitt, Prince William and Prince Harry.

He's written a book and does motivational speaking.

He lives his life literally one step at a time.

"It's a lot easier to look at what happened to me as not a negative or a positive. It's 'where's the next step?'

"That's one of the things you always have to think about when you're wearing prosthetics because they're different to normal feet.

"Once I start swinging my right leg, I can't stop it until the heel hits the ground. So I'm always looking down, thinking 'where am I going next?'."

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