"Sunday Bloody Sunday" is the opening track and third single from U2's 1983 album, War. The song is noted for its militaristic drumbeat, simple but harsh guitar, and melodic harmonies. One of U2's most overtly political songs, its lyrics describe the horror felt by an observer of The Troubles in Northern Ireland. The title and critically charged lyrics have been attributed to Bloody Sunday, which occurred on January 30th, 1972, when British paratroopers opened fire on unprovoked unarmed Catholic Northern Irish independence marchers. Formal government apologies were eventually issued to the families of the 14 killed and 13 injured. http://www.britannica.com/EBchecked/topic/726532/Bloody-Sunday
The single was released in March 1983 in Germany and The Netherlands only; "Two Hearts Beat As One" was released instead in other territories. Along with "New Year's Day", the song helped U2 reach a wider listening audience. It was generally well-received by critics on the album's release.
The song has remained a staple of U2's live concerts. During its earliest performances, the song created controversy. Bono reasserted the song's anti-hate, anti-sectarian-violence message to his audience for many years. Today, it is considered one of U2's signature songs, being one of the band's most performed songs. Critics rate it among the best political protest songs, and it has been covered by over a dozen artists. It was named the 268th greatest song by Rolling Stone on their list of the 500 Greatest Songs of All Time.