Protection and Conflict: Historical Tests of Commercial Liberalism, 1865-1992.

While a strong empirical consensus has emerged in international relations that commerce promotes peace, this literature still faces an important historical challenge. The first period of globalization dating from the middle of the nineteenth century until 1914 stands out as perhaps the Achilles' heel of liberal international relations theory. Dramatic economic integration in the previous half century failed to prevent the outbreak of war in 1914. In this paper, we respond to this criticism with the help of a newly constructed data set and a theoretical revision grounded in standard trade theory that leads us to rethink and compare some of the more popular causal mechanisms offered to explain a liberal peace among states. Tested across multiple research designs, we find that the expansion of free trade, or a reduction in barriers to commerce, decreased the willingness of governments to initiate military conflict against other states from 1865 until 1918. The basic logic of commercial liberalism holds during this first era of globalization: free trade promotes peace. [ABSTRACT FROM AUTHOR]