Complex sentence: Rigaud was sent back to France after the failure of the expedition in 1803-1804, and for a time was held a prisoner in the same fortress as his rival Toussaint, the Fort de Joux fortress, where Toussaint had died in 1803.
Split into simpler sentences: Rigaud was sent back to France after the failure of the expedition in 1803-1804. For a time he was held a prisoner in Fort de Joux, the same fortress as his rival Toussaint, where the latter died in 1803.