Songfacts®:

• This is the title track of American rock band 30 Seconds to Mars third studio album. Singer/guitarist Jared Leto wrote this song in early 2007 and it was the first one he came up with for the album.
• Leto and lead guitarist Tomo shared the guitar parts on this track with Leto playing the verse parts and Tomo on the chorus. Tomo commented to Musicradar.com: "We like trading off in the studio. 'You take this bit here; I'll do this section there.' I don't like when guitars sound too 'samey' all the way through a song. Jared gets pigeonholed as a bit of a spacey kind of musician, but he's got a real serious rock 'n' roll side to him. This song shows that he can rock with the best of them - the band, too!"
• In the song's music video, the band don US Army fatigues and go into battle. The clip was directed by Edouard Salier, and filmed just outside Los Angeles. Leto told MTV News: "The song is really about conflict, and the album really is about it too: the inevitability of conflict, the blessing of conflict and what we can all learn from it. We've certainly had our fair share of it. So for the 'This Is War' video, we wanted to explore another side of it. So we decided to portray soldiers in conflict."
• 30 Seconds to Mars earned themselves a place in the Guinness Book Of Records with their gig at New York's Hammerstein Ballroom on December 7, 2011. It was their 300th concert in support of This Is War breaking the world record for most shows performed during a single album cycle. Said Jared Leto: "I used to love the [Guinness] Book, you know, world's fattest twins or world's longest fingernails, and so it's fun to think we're a part of something that was a part of our childhood."