Executive orders are one of the most common ways a president can unilaterally implement policies. Only one president failed to sign any, and each president since 1880 signed over 100 of them. However, only three of the last 15 presidents signed an executive order on their first day in office, including President Trump, who did so at the start of both administrations. We will review the history of executive orders, how they work, how they can be challenged, and how they differ from other executive actions, including presidential memoranda and proclamations. Some notable executive orders occurred during times of war. We will examine how the courts deferred to the president in some situations and sought to restrain him in others.