Country superstar Keith Urban scored a No. 1 hit with his early-2017 Carrie Underwood collaboration "The Fighter," a song that also won Vocal Event of the Year at the 2018 ACM Awards. The track immediately resonated with fans, and Urban says its subject matter was deeply personal to his own life as well.

"It was such an easy song to write because it was borne of real conversations that [Nicole Kidman] and I had before we got married," the singer, who wrote the track with songwriter busbee, explained to The Boot and other media outlets at a recent press conference. "[It's about] some of those fears she had about it, and me wanting to be able to make vows to her, promises I knew I could keep -- like, 'Just give me a chance, give me a chance,' you know?"

Urban notes that the lines in "The Fighter" reflect the promises people make when they're in a relationship that they want to last forever: "In a lot of ways, the song feels like vows -- like, 'This is what I promise I'll be and do. I'll take care of you and keep the world away,'" he says. "It was very easy to write from that perspective."

From that standpoint, it felt natural for Urban to structure the song as a conversation between two people, and he knew from the beginning that he wanted to the song to feature a call-and-response phrasing between him and a female vocalist. "It started from literally just wanting to write a duet, which I'd never done before," he explains, "and a very specific duet."

While "The Fighter" may have been the first duet Urban wrote, his latest album, Graffiti U, includes no fewer than three male-female duets: "Drop Top" with Kassi Ashton, "Coming Home" with Julia Michaels and "Horses" with Lindsay Ell. With "Coming Home" as his newest No. 1 hit, Urban's fans seem to like hearing his duets as much as he likes singing them.

"[Female vocalists] can sing higher choruses. Some [duets] come about literally from that," Urban explains with a laugh. "But there's such a great balance of things, I find."

On the day he wrote "The Fighter," while in the car on the way to meet busbee for their writing session, Urban says he was inspired to write a duet when he heard pop singer Charlie Puth's collaboration with Meghan Trainor, "Marvin Gaye," come on the radio. "And the very next thing I thought about was -- this is weird -- "Paradise by the Dashboard Light"? By Meat Loaf? It's so obscure, but the reason why I love that song is because they talk back and forth to each other. It was a conversation: answer, question, question, answer. I get chills; I was so taken by that.

"That song has always stayed with me," Urban continues. "But I thought it'd be great to write a call-and-response thing between a guy and a girl."

It took quite a while after Urban recorded his vocals for Underwood to get a chance to cut her part of "The Fighter;" in the meantime, busbee had sung the other half of the call-and-response lyrics. When Urban finally heard Underwood sing on the track, though, he knew his instincts to record the song as a duet had been right.

"When he finally got to record Carrie was when I was shooting the video to "Wasted Time" out in California," Urban recalls. "I took a break from shooting the video, FaceTimed them, and that was the first time I heard her singing, through the FaceTime. They were listening to playback, and when I heard her voice singing that chorus, I was just elated [over] how it worked out. She was perfect for the song."

See Keith Urban + More Country Stars Then and Now

Unforgettable Keith Urban Moments

More From Kalamazoo's Country