THE U.S. imposed sanctions on leaders of militant groups over the taking of hostages, including Americans, in West Africa, the Treasury and State departments said. WHY IT'S IMPORTANT The sanctions on leaders of the West African branch of al Qaeda, called Jama'at Nusrat al-Islam wal Muslimeen (JNIM), and Islamist militant group Al-Mourabitoun come as Washington has sought to deter and punish detentions of U.S. citizens abroad. West African countries have been destabilized in recent years by Islamist insurgencies that took root in Mali in 2012 and spread across the Sahel region despite costly, international backed-military efforts. KEY QUOTES "We will not hesitate…