By Jim Webb, from the March/April issue of The National Interest. Webb, a Virginia Democrat, served in the U.S. Senate from 2007 to 2013.

In matters of foreign policy, Congress, and especially the Senate, was designed as a hedge against the abuses exhibited by European monarchs who for centuries had whimsically entangled their countries in misguided adventures. The Constitution would prevent the overreach of a president tempted to risk our country’s blood, treasure, and international prestige. Congress was given the power to declare war and appropriate funds. The commander in chief would execute policies within the boundaries of legislative…