In 1978, Jacob formed the band Rising Force together with guitarist Yngwie Malmsteen. Three years later Jacob joined the band Force, which later changed its name to Europe, replacing John Levén, who took Jacob's place in Rising Force. During his time in Force, Jacob wrote the song "Black Journey Through My Soul" together with vocalist Joey Tempest. The song was eventually included on Europe's second album "Wings of Tomorrow", retitled "Scream of Anger". After spending three months in Force, Jacob traded places with John Levén again, who apparently had issues with Malmsteen. In 1985, Jacob returned to Malmsteen's band to play on the album "Marching Out" and parts of the following US tour.