Songfacts®:

• Imagine Dragons wrote this song for the Transformers: Age of Extinction movie. "They reached out and asked if we wanted to do something with (composers) Hans Zimmer and Steve Jablonsky, who are two of our all-time favorites - they're legends," vocalist Dan Reynolds told Billboard magazine. "It's incredible to work with them. We all grew up watching the Transformers cartoon, it was part of our youth, we're children of the '80s."
• The idea for the theme song came to Reynolds after watching parts of the movie with director Michael Bay. From there, the band wrote the tune with Steve Jablonsky and Hans Zimmer. "As we were in the room with them we'd be playing something," Reynolds said, "they would change one note and suddenly it would give this feeling of remorse, or feeling of happiness."
• Reynolds told Billboard that the band were originally reluctant to write the theme for the film, despite Michael Bay hand-picking them. "Originally, we didn't think we were going to be able to do it.," he said "We've been saying no to everything because physically we just haven't had time. But we got into a room with him, he told us the story and I had a melody that rang in my head right from that moment. Some songs take a year to come together, but 'Battle Cry' wrote itself very quickly."
  
  "It was cool to compose a song in a more cinematic way," he added. "We tried to create something to benefit a visual as opposed to just being true to the song."