New U.N. operations in the Sahel present unprecedented challenges for U.N. peacekeeping. They involve the United Nations directly in the struggle against transnational Islamist terrorism, weapons proliferation, and illicit trafficking by international organized crime. The United Nations must operate in countries with harsh terrain, vast expanses, poor communications, and porous borders. In response, the Security Council adopted more robust mandates based on the peace enforcement provisions of the U.N. Charter. In Mali, the United Nations joined the African Union, the European Union, and France, whose forces conduct combat operations, while the United Nations used helicopter gunships and armed police units to protect civilians. In the Central African Republic, U.N. Police are authorized to control violence and arrest offenders. For the United States, there is new interest in U.N. peacekeeping and its importance to U.S. national security interests.