It was referred to by Spin as sounding "like an out-take from the Dookie sessions".About.com's Bill Lamb said the song was "standard issue Green Day", "not a stroke of genius" and "not on par with their last album", but said it was a "great appetizer" for one of the most eagerly awaited albums of 2009.Pitchfork Media described the track as having "pedantic stiffness" and "nothing more than a rote protest song preaching to the converted".Rolling Stone called the song one of the highlights of the album, praising the punk-oriented sound and calling it a "Clash-size bootboy chants".Billboard said that "The lead single from the band's new release, "21st Century Breakdown", finds the group just as politically charged as last time", but also said that "While the subject matter is broad and may be missed by some, "Enemy" has enough charm to amp up the airwaves until (21st Century) Breakdown is released."
The music video was directed by Motion Theory's Matthew Cullen (who helmed the video for Weezer's "Pork and Beans" in 2008), and it premiered on MTV and other stations across the globe on April 24, 2009. In the video, the band is performing at night on a stage in a field surrounded by a barbed wire fence. Shots of the band are also frequently seen through night visionclosed-circuit cameras that surround the field, as well as on helicopters that patrol the area with searchlights. The final chorus of the song shows fire burning behind the band in silhouettes of the band members (Billie Joe has a man with a guitar behind him, Tre Cool has a man playing the drums behind him, Mike Dirnt has a man playing bass behind him). The video was shot in Downtown Los Angeles.
^"Concert review: A Green Day reckoning". July 11, 2009. Archived from the original on July 15, 2009. Retrieved July 12, 2009. Before singing the current radio fave "Know Your Enemy," he said, "The day we recorded this song was the first day of the Republican Convention. The Republican Convention was here, right? We got those [bleep] out of office, right?"