LONDON — The Giants have shown remarkable grit and determination this season when playing in the United States. They took that fighting spirit overseas and showed an international audience — and the Packers, from Green Bay, Wis. — that this is a new and quite improved Giants operation.

The Giants trailed 17-3 in the second quarter and 20-10 at halftime against Aaron Rodgers, and it looked as if this would not be a fruitful trip across the pond for coach Brian Daboll’s club. What transpired in the second half was stunning. The Giants on defense pitched a shutout. Daniel Jones gutted out yards and points. Saquon Barkley was forced out with a shoulder injury and returned, not wearing a cape but playing like Superman.

Barkley scored the game-winning touchdown with 6:08 remaining and then turned the game over to their largely no-name defense. Rodgers moved the Packers to the Giants’ 7-yard line but on fourth down his pass was deflected up and into the air by blitzing safety Xavier McKinney. The ball fell harmlessly to the grass at Tottenham Hotspur Stadium with 1:11 remaining and soon after the Giants secured an improbable 27-22 comeback victory.

And just like that, the Giants are 4-1, matching their win total from the entire 2021 season.

“I mean, it’s putting the world on notice,’’ rookie edge-rusher Kayvon Thibodeaux said. “We’re a hard-nosed team that’s gonna fight to the end. We’re gritty. We’re gonna fight for each other and we don’t care who we’re going against. We’re gonna keep playing to the end.’’

This latest victory was the most impressive of all for the upstart Giants. Daboll erupted with joy on the sideline after the final play and pumped his fists to those in the crowd of 61,024 wearing blue.

Out of nowhere, the Giants dominated the second half, outscoring the Packers 17-2, with the only points allowed a giveaway safety with 10 seconds left. They did it without their best cornerback, Adoree’ Jackson, who did not play in the second half with neck and knee issues.

Barkley ran 13 times for 70 yards. Jones, playing despite a sprained left ankle, was incredibly tough. He completed 21 of 27 passes for 217 yards and ran 10 times for 37 yards. He refused to allow the injuries to teammates around him and the deficit in front of him to deter him from finding a way.

“He’s a super tough guy, super tough leader,’’ rookie tight end Daniel Bellinger said. “Every time he comes in, he pushes me to be better when I see that kind of stuff. He pushes the whole team to be better.’’

After punter Jamie Gillan wasted time and then ran out of the end zone, rather than kick the ball from his own end zone, the Packers got the ball back with seven seconds to go, Rodgers rolled out for one of his patented Hail Mary heaves and Oshane Ximines was there to deck Rodgers, ending one of the most emotional Giants’ victories in years.

“I ain’t gonna lie it meant a lot,’’ Ximines said. “I hope I got a picture, that’s all I want.’’

Make no mistake, this was a road game for the Giants, with the crowd composed mostly of Packers fans — it was their home game. By the end though, the Giants fans who made the trans-Atlantic journey were in full-throat mode.

“A lot of Packers fans,’’ Daboll said, “but at the end of the game it felt like a home game.’’

Barkley left the game with 3:15 remaining in the third quarter. He caught a pass and was dragged down by linebacker DeVondre Campbell, with Campbell landing on Barkley and Barkley immediately motioning that something was wrong. He came off the field, headed into the medical tent and when he emerged out of the tent his helmet was taken away from him. Eventually, he got it back.

“Just got banged up,’’ Barkley said.

The Giants were down 17-10 when Barkley departed and Jones was left with a remarkably makeshift collection of skill players around him. Yet Jones persevered. He put together a 15-play, 91-yard drive that took 8:07 off the clock, handing the ball to Matt Breida and throwing it to practice squad call-up Marcus Johnson and Bellinger and backup tight end Chris Myarick and David Sills. It was fitting that Gary Brightwell, a seldom-used running back, muscled his way into the end zone on a bullish 2-yard run to pull the Giants even at 20-20 with 10:08 remaining.

Next, the Giants got big defensive plays from Nick McCloud and Fabian Moreau — yeah, who? — to force a three-and-out and took over on their own 40-yard line. What followed was wild. Barkley returned, took a short pass from Jones and juked and sprinted his way to a 41-yard gain. To end the drive, Barkley took a direct snap out of the Wildcat formation and was not stopped, beating every Packers defender to the right corner of the end zone. It was 27-20 with 6:08 left.

The Giants were creative on both sides of the ball. Darius Slayton came in with one catch in the first four games but he was Jones’ go-to target. The lone touchdown of the first half for the Giants came after Barkley on a direct snap rumbled for 40 yards and Slayton then caught passes for gains of 10 and 9 yards. To get into the end zone, Jones pitched the ball to Barkley, who flipped it to Bellinger on a double-reverse. Bellinger had the option to throw it to Jones or tight end Tanner Hudson but he decided to run for it and scored to make it 17-10 with 1:15 left in the second quarter. But Rodgers hooked up twice with Randall Cobb and the Packers added a field goal as time expired in the first half to go ahead 20-10.

The second half was all Giants.

“We’re gonna play to the end, we’re gonna play for 60 minutes, we’re gonna play hard,’’ McKinney said. “We got a lot of good dudes, a lot of good players. We knew what we had before, we didn’t really need anybody to tell us what we have or didn’t have.’’

What the Giants have, after five games, is a record of 4-1.