The band was founded in Fort Worth, Texas by ex-Terminal members Ryan Conley (drums), Lucas Starr (bass), and James Erwin (guitar), along with Micah Kinard (unclean vocals) and former Between the Buried and Me guitarist Shane Blay (guitar, clean vocals). Taking their name from a passage in the New Testament's Epistle to the Ephesians ("Therefore it says, 'Awake, O sleeper, and arise from the dead, and Christ will shine on you"), the newly-minted quintet issued their debut EP The Armored March in late 2006. They were scooped up by Solid State Records the following year, with whom they released their first full-length effort When I Am God, which featured re-recorded versions of the songs from The Armored March, alongside several new recordings. Conley left after a tour with Norma Jean in support of the album, and was replaced by new drummer Matt Davis, who made his first studio appearance on 2009's ambitious Son of the Morning. A concept LP concerning an apocalyptic battle between God and Satan, it was the band's highest charting outing to date, cracking the Billboard Top 200 albums chart and rising to the upper echelons of the hard rock and Christian albums charts. Bassist Starr was the next to leave the fold, making room for Nate Grady, who made his debut on 2011's Children of Fire. Another narrative-driven set, this time dealing with the aftermath of the rapture that occured at the end of Son of the Morning, the album made an even stronger showing than its predecessor, climbing to number one on the hard rock albums chart. Guitarist James Erwin announced his departure in 2012, resulting in Grady taking over guitar duties while passing the bass to Johno Erickson, formerly of Sky Eats Airplane. Having fulfilled their contract with Solid State, the band used crowdfunding to help underwrite their next release. The resulting sci-fi-themed EP The Titan arrived in 2013. Later that year Oh, Sleeper would go on hiatus, allowing Shane Blay to join up with members of As I Lay Dying to front a new project called Wovenwar.
In 2017 the band returned to the studio and released the single "Oxygen", with a second single, "Decimation & Burial", arriving the following year. 2018 also saw the group return to Solid State Records and announce the impending arrival of a new full-length effort -- former bassist and co-founder Lucas Starr passed away in December of that year after a four month battle with cancer. A third single, "Fissure", was released in January 2019, with Bloodied/Unbowed arriving later that July. ~ James Christopher Monger, Rovi