France on Thursday opened the door to possibly joining airstrikes in Syria just hours after an Algerian Islamist group beheaded a French tourist in retaliation for Paris’ military action against ISIS militants in Iraq. France has repeatedly ruled out taking part in air action in Syria where ISIS has its power base. It fears that strikes against militants there would leave a void that only Syrian President Bashar Assad’s forces could fill, making it difficult for “moderate” rebels to counter the more organized Syrian army.