Which war did Bill Clinton start again?
Generally, the US/NATO-led interventions in the Balkans, most notably the US-led NATO-Serbia war, after explicit Congressional disapproval.
Though I suppose those could be excluded since they were interventions in existing conflicts.
Of course, there's probably some dispute over whether intervening to prevent genocide, either in general or in the specific manner it actually occurred under Clinton in the Balkans, is really a negative.
Of course, compared to Iraq invasion it was a small scale operation, but is still generally considered Obama responsibility (although of course primarily Sarkozy and Cameron responsibility).