This week, the United States will celebrate 100 years of women’s suffrage. The Nineteenth Amendment, ratified on August 18, 1920, and certified as part of the Constitution on August 26, 1920, granted women the right to vote. In practice, many women—particularly Black women in the South—could not exercise their right to vote until decades later. Still, women’s suffrage altered the political landscape in the United States. And as it spread across the democratic world in the first half of the twentieth century, women’s suffrage altered international politics, as well—in particular, by reducing the likelihood of interstate conflict, especially between democratic countries.
That democracies are unlikely to fight one another is one of the few widely accepted findings in international relations. Democracies do fight with nondemocracies, but they are less likely than nondemocracies to initiate such conflicts. What explains this “democratic peace” is still a matter of debate. Is it democratic norms? Democratic institutions? International trade? Or some combination of these factors? In new research to be published this month in the journal International Organization, we show that women’s suffrage is an important contributor to the democratic peace. Women are less likely than men to support the use of military force. Their pacific preferences don’t always prevail within democratic institutions, but our research shows that democratic states with women’s suffrage initiate fewer disputes with all countries and that they experience more peaceful relations with other suffrage democracies.
