This is not just about the economy, though; it's also about global security. In the 1990s, nearly half of all peace agreements failed within the first five years, according to the Human Security Report Project. These deals are generally struck by a small number of male military and political leaders shielded from war's impact on daily life. Women, meanwhile, endure much of the residual violence and poverty caused by armed conflicts, and they bear much of the burden of rebuilding families and communities. They are often excluded, however, from both the negotiating table and the governments charged with sustaining peace. Less than 8 percent of the hundreds of peace treaties signed in the last 20 years were negotiated by delegations that included women, and according to the World Economic Forum, women hold less than 20 percent of all national decision-making positions.

Excluding women from these negotiations exacts a measurable cost. In 1994, for instance, women were far from the minds of the men who, with U.S. support, signed the Lusaka Protocol that ended two decades of civil war in Angola. The commission established to implement the protocol consisted of 40 men -- and not one woman. Women were also left out of demobilization programs for ex-combatants because the definition of "combatant" did not consider the thousands of women who had been kidnapped and forced to work as military cooks, messengers, or sex slaves. Demining efforts focused on roads and failed to target the fields, wells, and forests where women grew crops, fetched water, and gathered firewood. And following a conflict in which rape was used as a weapon of war, the male negotiators granted each other amnesty for the crimes they had committed against women. Just four years later, war began anew.

We do not want to see history repeating itself. Last December, the administration launched a national action plan on women, peace, and security, which expands U.S. efforts to include women in conflict prevention, peace negotations, and reconstruction. Still, the exclusion of half the world's population continues to threaten many countries. In Egypt last year, women marched on the front lines of the protests, often leading their fathers, brothers, and husbands into Tahrir Square. A year later, the courageous women of the Arab Spring fear not just that progress on women's rights will halt, but that the rights they currently enjoy will be rolled back.

Or consider Afghanistan. Although the number of women attending school and serving in parliament and on local peace councils has increased dramatically over the past decade, the country remains the world's most dangerous for women in terms of health, violence, and lack of economic resources. The United States must continue to insist that insurgents who want to reconcile must commit to protecting the rights embedded in the Afghan constitution -- including those for women. There may be some who, in the interests of getting a deal done, consider women's rights negotiable. But this is a red line that cannot be crossed; any peace that is made by excluding more than half the population is no peace at all and will not last.

In all circumstances, and especially in the most challenging ones like those in Afghanistan, the United States must remain a vital voice for women and girls not just because it is the right thing to do but because it is the smart thing to do. Give a small-businesswoman access to capital and training, and she can become a powerful contributor to GDP growth. Include women in governments and peace talks, and they can help ensure that ministries are better run and peace agreements are sustained. Educate a girl, and she will be more likely to raise healthier and more educated children -- and end the cycle of poverty.

Secretary Clinton has championed the use of "smart power": deploying all the tools at America's disposal to advance national interests -- not just military might, but also diplomacy, development, and America's enduring values. Advocating for women's full economic, social, and political participation around the world is one of the most potent weapons in America's smart-power arsenal. And it's one we shouldn't even hesitate to unleash.

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