Whitesnake became very popular in the UK, Europe, and Asia, but not in North America. In 1984, the album "Slide It In" finally entered the US charts (reaching #40). But it did not reach high enough to be considered a hit. When "Slide It In" was going to be released in the US, Coverdale made a calculated attempt at changing Whitesnake's sound and look. He recruited John Sykes from the remnants of Thin Lizzy for this. Sykes brought a more contemporary, aggressive guitar sound with him. He also had good stage manners to match. In 1985, Sykes and Coverdale started working on new songs for the next album. But Coverdale soon contracted a serious sinus infection. So he could not record that year. Doctors said he might not be able to sing again. Coverdale eventually recovered, and recordings were continued. But before their upcoming album was fully recorded and released, Coverdale had dismissed Sykes from the band.