The United States began its existence as an act of foreign policy. It is no exaggeration to say that the nation owes its very existence to the successful pursuit of war and diplomacy. ‘First principles’ explains that over a period of forty years, from the outbreak of revolution in 1775 to the end of war with Britain in 1815, the founding generation established and consolidated a new nation by responding to a series of international challenges. Along the way, they established a set of first principles of foreign relations: namely, unilateralism, exceptionalism, and expansionism. These would shape Americans’ engagement with the wider world for centuries to come.