War and emergency powers have existed over the centuries in different countries, raising questions about the political authority related to them. 'US Congress' Powers under Debate' illustrates how war and emergency powers have been understood and what kind of concepts and argumentation have been adopted to define these powers in US political debates from the 1970s to the 9/11 terrorist attacks and the Donald J. Trump administration. Its aim is to show the oversight Congress may have over presidential powers in exceptional situations and thus to offer a novel approach to the study of war and emergency powers.