Billy Joel returned to pop songwriting in 2007 with an unexpected surprise: a one-off protest song called “Christmas in Fallujah.”

Only the second pop tune Joel had released since 1993’s River of Dreams, “Christmas in Fallujah” featured the singer and songwriter putting a sad spin on the ideas and emotions found in John Lennon’s “Happy Xmas (War Is Over).” Released as an iTunes exclusive on Dec. 4, 2007, “Christmas in Fallujah” was punctuated with fiery and tough anti-war rhetoric.

The topic and dark tone weren’t the only surprises. The biggest shock: The Piano Man didn’t even sing on the song.

Written by Joel, the song featured 21-year-old unknown Cass Dillon (who would go on to play guitar with and date Joel’s daughter Alexa Ray) on lead vocals. On Dec. 1, Dillon joined Joel onstage to debut “Christmas in Fallujah” in front of a packed house at Chicago’s Sears Centre. With the full power of Joel’s live band, Dillon blasted out the grunge- and “Kashmir”-influenced tune singing, “We came to bring these people freedom / We came to fight the infidel / There is no justice in the desert / Because there is no God in hell.”

Showing their support for the troops, Joel and Dillon had soldiers join them onstage for the song's debut. Behind the band on the stage, the troops shouted “oo-ra” along with the song’s refrain. Just like Lennon’s signature Christmas song, Joel and Dillon’s work confronted a war the American public had long soured on.

On his website, Joel noted that a flood of letters he received from the U.S. forces fighting in Iraq inspired him to write the song. But after finishing the composition, the 58-year-old artist felt a young man should give voice to the lyrics.

“I didn't feel I was the person to sing this song,” he wrote. “I thought it should be somebody young, about a soldier's age. I wanted to help somebody else's career. I've had plenty of hits. I've had plenty of airplay. I've had my time in the sun. I think it's time for somebody else, maybe, to benefit from my own experience.”

Joel's guitarist Tommy Byrnes discovered Dillon during a set at the Drama Cafe in Baldwin, N.Y.. A college dropout trying to navigate the competitive singer-songwriter scene, Dillon was struggling to find fans. As soon as Byrnes connected the unknown and the icon, the pair clicked. Joel flew Dillon out to San Francisco to record “Fallujah” on Veterans Day.

Putting his money where his mouth is, Joel donated the proceeds from the song to Homes for Our Troops, a nonprofit organization that builds specially designed homes for soldiers returning from Iraq and Afghanistan with severe disabilities.

Nevertheless, Joel continued to struggle with the idea of a protest song. “I never liked when a rock star got up onstage and told people how to vote,” he told Rolling Stone at the time. “I find it insulting. But I believe if an artist feels strongly about something, it should be reflected in their art. Ultimately, everything's political. Even love is political.”