The United States conducts modern peace operations to prevent, contain, or resolve regional conflicts that may pose threats to national interests. The facts upon which strategic decisions and agreements with involved parties are based may greatly differ from the realities the operational and tactical level commanders may find once they are deployed. Additionally, the operations these commanders are tasked to perform may result from long-term, maturing crises, such as one in which a peacekeeping operation is needed. Conversely, the operation may seek to relieve a humanitarian crisis, which can be a short notice rapid reaction effort. Finally, the commanders may find themselves faced with a combination of the two, creating a "complex contingency." As a joint task force commander, you must grasp the nature of the operating environment in order to successfully complete the mission. As the 21st century approaches, the nature of conflict continues to change from that of interstate war to that of intrastate conflicts. US military traditional training has taught leaders about the impact that the mission, terrain and weather, troops and support available, and time available have on operations. Today, successful military operations also include consideration of other factors and their impact on those operations.