Arnold boldly turned to substitute goalkeeper Andrew Redmayne moments before the shootout at Ahmad bin Ali Stadium in Doha on Tuesday night (Wednesday AEST), substituting the Sydney FC shot-stopper into the game at the expense of captain Maty Ryan.
Redmayne then danced his way into Australian sporting history with the winning save as Australia took out the shootout 5-4 to seal their place in November's World Cup in Qatar.
The decision to turn to Redmayne came close to the end of 120 goalless minutes after Australia had stunned the more-fancied Peruvians with their fight and organisation.
Peru had their chances to win the game, especially when substitute Edison Flores hit the post with a header in extra-time, but in the shootout Australia held their nerve to achieve something many back home didn't think was possible.
"I"m quite speechless because no-one in Australia gave us a chance," Arnold said.
"I'm accountable for the results.
"But I'm a coach and manager, my style is management and getting the best out of players and doing things face-to-face. Being on the training pitch with them.
"During COVID having to train and try to do meetings and talk to the players on Zoom meetings, it's not my style.
"I didn't like it at all and to be honest, there was times when I nearly walked away because it's not my style of coaching.
"The only reason I didn't walk away is because of the players and the sacrifices they've made."
Everything was against Australia heading into the contest.
Peru, the world No.22 were highly fancied to beat the Socceroos as they did at the 2018 World Cup, especially with approximately 12,000 fans cheering them on in the stands compared to roughly 500 Australian supporters.
Having battled through 120 minutes, the shootout began horribly for the Socceroos with Peru captain Pedro Gallese saving Martin Boyle's opener.
From there though the Socceroos didn't miss with Aaron Mooy, Craig Goodwin, Ajdin Hrustic, Jamie Maclaren and Awer Mabil all scoring from the spot before Redmayne's moment to shine.
Redmayne dived to his right and saved Peru substitute Alex Valera's penalty to spark celebrations for the Australians in front of their small supporter block.
Earlier, after a spirited opening, the first shot on target for either team came via Hrustic in the 81st minute but his long-range free kick was easily claimed by Gallese.
Four minutes later, left-back Aziz Behich picked up a loose ball and beat two Peruvians before shooting just wide from outside the box.
Hrustic nearly stole the win for Australia in the 88th minute when he was found by substitute Mabil's cutback but Gallese just managed to keep the midfielder's shot from squirming in.
Flores had Peru's first shot on target in the first period of extra-time before his header hit the post.
Arnold then turned to Redmayne moments before the final whistle, in a decision which will now go down in Australian sporting folklore.
"Guus Hiddink, I was his assistant in 2005," Arnold said of Australia's famous shootout win over Uruguay in Sydney.
"He was going to do the same thing with Mark Schwarzer and take off Schwarzer and put on Zeljko Kalac.
"It was a risk, but it worked out."
