One of the traps we fall into when studying history is that it's often impossible to comprehend that the world hasn't always been the way it is today. In this age of globalization Americans enjoy unprecedented prosperity, so we tend to assume that previous generations did as well.

But the fact is that human history is an uninterrupted story of inequality, injustice and poverty. Seventeen percent of the world's population lived on less than a single U.S. dollar per day in 1970 - in inflation-adjusted dollars, using purchasing-power parity terms. Three decades on, in 2000, the proportion was 7 percent. It's only in the second half of the 20th century that humankind began to turn the tide in the war on poverty.

What few notice is that the American military has played a leading role in the fight against poverty, often without firing a shot.

From Germany and Japan through South Korea, Taiwan, Vietnam, Bosnia and now Iraq, Americans have sacrificed blood, time and treasure to resist tyranny, protect freedom and spread prosperity. Under our security umbrella, several of those countries have become global economic juggernauts.

Our military fought to protect South Korea, and the outcome there highlights the importance of our troops. That country is an Asian tiger, with steadily expanding opportunities for its people. Meanwhile, satellite photos reveal a North Korea that's literally stuck in the dark ages; while the southern half of the peninsula blazes with electricity every night, the northern half is almost completely dark.

Even when we lost the shooting war, Americans won the war of ideas. Vietnam, for instance, has liberalized its economy and wants to join the World Trade Organization.

In fact, the longer American troops are in a country, the better that country does. In a working paper, Dr. Garett Jones of Southern Illinois University and I found that the presence of 10,000 American troops over many decades leads to a major increase in economic growth every year - after other causal variables are considered.

An active American security umbrella enhances investment and spreads our ideals. Our soldiers promote universal values, including transparent government authority, and they help enforce vital human rights, such as property and voting rights. Their presence around the globe has allowed natives of dozens of countries to build successful democratic societies.

Everyone agrees that a soldier's sacrifice implies a life unfulfilled. And beyond those who paid the ultimate price there are millions of Americans who have sacrificed years of their lives to serve overseas even in peacetime. On this Memorial Day weekend we should honor their service and remember the benefits they've helped deliver to all of us.

To paraphrase John Stuart Mill: War is an expensive thing, but not the most expensive of things. A man unwilling to pay any price for the well-being of others is a sad creature indeed.

As we've learned in Iraq, regime change isn't cheap. But if history is any guide, the returns on sending American soldiers to the Middle East will be positive.

Tim Kane, Ph.D. is a U.S. Air Force veteran and the director of the Center for International Trade and Economics at the Heritage Foundation