Out of Hamilton, Ontario, Canada, Threat Signal arose when cousins Jon and Rich Howard recruited local shredder Kyle McKnight in late 2003 and began to record demo material. Former guitar teacher Marco Bressette joined Threat Signal on bass in August 2005, and George Parfitt was the final member to complete the band in January 2006. Rich Howard decided to part ways with the act in August 2006 to pursue other interests. Bressette filled his position on guitar and Pat joined the band on bass. In April 2004, Threat Signal released their first demo Rational Eyes shortly later. With the success of Rational Eyes, the band was contacted by various record labels that were extremely interested in their music. This prompted Threat Signal to release three more songs onto www.garageband.com titled One Last Breath, Inane, and A New Beginning.
In September 2005 Threat Signal flew to Los Angeles to record their debut album, Under Reprisal, with producer Christian Olde Wolbers of the band Fear Factory. The band would combine the complexity of old school and European Thrash Metal music with de-tuned, technical syncopation, as well as melodic singing and musical passages. Threat Signal took influences from highly establish ed bands such as Soilwork, Fear Factory, Pentera, Meshuggah, and Devin Townsend.