As reported by Ultimate Classic Rock, Bryan Adams told music historian Eddie Trunk on “The Eddie Trunk Podcast” about the experience of writing “War Machine” for KISS. “I went down to Los Angeles. Gene [Simmons] had a guitar riff, but he didn’t have a song. I thought it was a pretty cool guitar riff,” Adams said. “I didn’t finish the idea when I was in L.A., but I took it back to Vancouver.” Back home in Canada, he and Jim Vallance got to work and came up with “War Machine.” 

On his website, Vallance quoted Gene Simmons’ notes from the KISS box set in which he noted, “Adams and Vallance added some chordal passages and the basic lyrical content, including the title, ‘War Machine.'” Per Vallance, he listened to the demo and commented, “it’s obvious that we contributed significantly more than some chordal passages and the basic lyrical content.” On the other hand, Simmons claimed a third of the royalties for “War Machine,” which was not the case for “Rock and Roll Hell.” Vallance later admitted, “That tells me Gene believed — and Bryan and I believed — that Gene’s contribution to ‘War Machine’ was more significant than I recall.”

While speaking with Eddie Trunk, Adams was pleased to hear that KISS still performs the song live and expressed his gratitude for the early career work from the band. “I would have been a broke songwriter and really grateful for the opportunity, and to this day, [I’m] still very grateful for the opportunity,” he said.