President Obama has finally made up his mind on Afghanistan — sort of. The clear decision and explanation that would either give meaning and rationale to our troops’ efforts or lay the foundation for a reasoned withdrawal has been put off, yet again.

It is almost heresy in conservative circles to say that changing circumstances — and not just President Obama’s indecisiveness — make it a good idea to start winding down America’s role in Afghanistan. This is heretical partly because of the noble instinct that if America goes into a war, she should finish it. It is also because the Left incessantly compares Afghanistan to Vietnam; we all realize how shallow this comparison is, so we seek to distance ourselves from the entire line of thought.

But the time has come to study another comparison: Afghanistan and Iraq. Conservatives who pride themselves on a realistic view of national security and military power must realize that while the Iraq War is still vital to national security and susceptible to the successful use of our military, the Afghanistan war is not.

Both wars were justified at inception — in the case of Afghanistan, to overthrow a government that refused to yield those who attacked the World Trade Center and the Pentagon; in the case of Iraq, to rid the world of a dictator who threatened neighbors while resisting nuclear inspection. However, now that the Taliban government has been overthrown and Saddam Hussein has been found, tried, and hanged, conservatives must weigh the strategic importance of each country to American national interest and the chances of a successful intervention.

Strategic interest is an overused concept, but a useful one if it is crisply and succinctly defined. During my time at the State Department, I read a paper that described Chad as a country “strategic” to the United States, and I thought: If Chad is strategic to us, every country in the world is strategic, and the concept is useless.

What’s a better definition? Given the globalized economy of today, a country is “strategic” when what happens there affects not just the country itself, or even a bordering country, but the region. In this light, a comparison of Iraq and Afghanistan is far more instructive than the oft-made comparisons of each and Vietnam.

Natural resources are one measure of strategic value, but they are important mainly when a country has a monopoly over a resource that has no substitute. Iraq is a big oil producer, although far from a monopoly; Afghanistan has no unique resource, unless you count opium.

Geography is another measure. Does the country sit on a key waterway, and if it were unfriendly, could it threaten shipping? Iraq on the Persian Gulf arguably fits, while landlocked Afghanistan obviously does not.

Perhaps the most important criterion is whether the country has a political or military impact on the stability and nature of government in neighboring states. Iraq is an Arab country bordering many other Arab countries. Whether Iraq is controlled by Islamic terrorists or has a stable quasi-democracy will affect the surrounding Arab states in their choice of government, their dispensation of oil, and whether they go to war. Iraq’s region possesses more oil than any other in the world. It sits astride key maritime transportation routes and affects the migration flows to many continents. It makes war-and-peace decisions that affect the United States and its allies.