Success in Afghanistan has always depended on more than the elimination of the al-Qaida network responsible for the Sept. 11 attacks. Protecting America's national security interests for the long term hinges on whether Afghanistan can secure a stable future.

On April 5, Afghans voted in a historic election — the country's first democratic transfer of power. Voters showed up to the polls after weeks of attacks by Taliban insurgents, who pledged to disrupt the process.

The turnout reaffirmed that the Afghanistan these militants seek to reclaim is much different than the war-torn nation the Taliban repressed more than a decade ago.

Afghanistan today is characterized by increased civic participation, rising life expectancy and a drastically improved education system.

The country achieved the fastest growth in human development in South Asia from 2000 to 2012, according to last year's United Nations' Human Development Report.

World Bank numbers show GDP growth averaged an impressive 9.2% for most of the past decade, reaching 11.8% last year. Particularly encouraging are advancements in human rights, especially for women.

More than 2.8 million girls are enrolled in school, and trailblazers like Fawzia Koofi, the parliament's first female deputy speaker, represent a burgeoning movement to end oppression and injustice.

It is no wonder, then, that a majority of Afghans are optimistic that their country is headed in the right direction. A recent poll found only 7% want the Taliban back in charge.

It is a shame that this message is not being accurately conveyed to the American people. To those who think Afghanistan was a mistake: Was it wrong to remove the Sept. 11 masterminds and stabilize the country so it would likely not happen again?

Progress has indeed come with sacrifice. More than 2,200 Americans have lost their lives, and thousands more have been injured.

But turning back at this critical hour could have severe repercussions, throwing away more than a decade of growth and diminishing the courageous service of our troops.

Success in Afghanistan is not a partisan issue. Democratic Sen. Carl Levin of Michigan, chairman of the Armed Services Committee, recently emphasized the high stakes "for our national security, for the security of our friends and allies ... for regional stability and, of course, for the Afghan people."

The war in Afghanistan can still be lost if we insist on giving up. A far preferable result is highly achievable — a stable partner that respects human rights and does not harbor terrorists. The outcome will depend largely on the presence — or absence — of American resolve. The U.S. needs to send a strong signal that we will not abandon allies who choose to side with us and who rely on us to be consistent.

The pending bilateral security agreement between the U.S. and Afghanistan is instrumental to ensuring security and stability. It assumes American and NATO forces will be involved after this year and has already been endorsed by the parliament and a virtually unanimous vote of the 2,500-member loya jirga representing all tribes and ethnic groups.

Gen. Joseph Dunford, the top U.S. commander in Afghanistan, recently told the Armed Services Committee that the security situation would swiftly deteriorate without a residual U.S. force.

A full withdrawal, said the general, would mean "abandoning the people of Afghanistan, abandoning the endeavor that we've been on for the last decade, and then providing al-Qaida the space within which to begin again to plan and conduct operations against the West."

The lessons of Iraq demonstrate the danger of withdrawing too soon. A reinvigorated insurgency in the Iraqi city of Fallujah is a reminder that our progress is fragile.

We should seize this opportunity for a historic partnership with Afghanistan, which is possible with only a small U.S. footprint. Afghanistan's success is also intrinsically linked to the stability of a nuclear Pakistan.

Although challenges still exist, the Afghan people have spoken for themselves about the future of their country. The election is a major milestone for the practice of democracy by generations who have never known the exercise of these freedoms.

In a war-weary world, it may be easy to forget why Afghanistan still matters. At this pivotal juncture, staying true to the mission for peace and stability is more important than ever.

This op-ed appeared in Investor's Business Daily on April 8, 2014.