Russia's invasion of Georgia has led to a more serious foreign policy discussion in the presidential campaign. As tensions rise in the Caucasus and violence once again erupts in Afghanistan, we should recall the lessons we learned from our response to earlier Russian adventurism. We must recognize now, as we learned years ago, that a strong military alone is not enough to ensure our long-term security.

In a scene near the end of the movie "Charlie Wilson's War," after the mujaheddin victory over the invading Soviet military, congressional appropriators turn down my request for funds to rebuild Afghanistan's schools, roads and economy. If we had done the right thing in Afghanistan then — following up our military support with the necessary investments in diplomacy and development assistance — we would have better secured our own country's future, as well as peace and stability in the region.

In reality, this decision played out over several years and involved many people, but the scene makes clear what a mistake we made. Sure, the problems facing Afghanistan and the region were tough — feuding warlords, the opium crop and the shift in our attention to the Persian Gulf War. But the Afghans, with our weapons, had done nothing less than help precipitate the collapse of the Soviet Union. And instead of intensifying our diplomatic and humanitarian efforts to help the Afghans meet their postwar challenges, we simply walked away — leaving a destroyed country that lacked roads, schools, and any plan or hope for rebuilding.

Into this void marched the Taliban and al-Qaida, and we all know what happened after that. Today, fledgling democracies — be it Afghanistan or Georgia — face similar danger. We simply cannot make the same mistake.

The lesson here is about more than the good manners of reciprocating a favor. It takes much more to make America safe than winning on the battlefield. Had we remained engaged in Afghanistan, investing in education, health and economic development, the world would be a very different place today. The aftermath of a congressional committee's decision so long ago has turned out to be a warning that America is not immune to the problems of the very poorest countries. In today's world, any person's well-being — whether he or she is in Kandahar, Kigali or Kansas — is connected to the well-being of others.

Yet, as we commit troops to the "war on terror," America's civilian institutions of diplomacy and development continue to be chronically undermanned and underfunded. We spend 1 percent of the federal budget on these critical elements of our foreign policy, compared with 22 percent on the military and weapons.

While I have always believed in and fought for a strong defense, I know that we cannot rely on the military alone to keep us secure. As the situations in Afghanistan and Georgia suggest, our future threats are likely to come from states that cannot meet the basic needs of their people. We can avoid the need to spend so much on our military — and put so many of our soldiers in harm's way — simply by investing more in saving lives, creating stable societies and building economic opportunity.

Defense Secretary Robert Gates was spot-on when he said last month, "The Foreign Service is not the Foreign Legion, and the U.S. military should never be mistaken for a Peace Corps with guns." We've got to get this right.

Robust investments in health, education and economic development are critical elements of our national security. I hope the message of our experiences in Afghanistan will resonate with the next president as he puts in place his strategic vision for America's role in the world.

Charles Wilson, a Democrat, represented Texas' 2nd District in the U.S. House from 1973 to 1997. He is an adviser to the Center for U.S. Global Engagement. He wrote this commentary for The Washington Post.