When I was young I was told that the United States and the Soviet Union had enough nuclear weapons in their arsenals to destroy the planet many times over. So when I reached the age where I was eligible to enlist in the military, I did not find myself stirred by a patriotic sense of duty to do my part to defend my homeland.

After all, with that kind of firepower available at the push of a button, I didn’t think that adding one more guy with a rifle would make much of a difference in a potential military conflict. I admit that I was pretty naive to think of the situation that way, but a lot of people were thinking the same way in the period between the end of the Vietnam conflict and the beginning or our current war with terrorism.

Back then, the world seemed to be made up of two monolithic superpowers whose quivers were full of so many terrible arrows that neither wanted to fire any of them. The only possible future seemed to be peace or total annihilation. It seemed ridiculous to even consider that a hostile force might invade our country, and after Vietnam it was widely assumed that we’d lost our taste for getting involved in far-flung conflicts in other parts of the world.

Of course, the world looks a lot different now. We have in fact been invaded, not by a traditional army but by small militias of hate who have used the openness of our society to sneak in and wound us in our sleep. They seek not to conquer us, but simply to make us suffer so much that we will withdraw our influence from the rest of the world, leaving it open for them to remake into their vision of a fundamentalist paradise.

Our enemy is not a single country, but little pockets of evil scattered throughout many countries. Our nuclear weapons are not much use against these armies — they are too spread out to strike effectively without decimating the planet. We have to send men and machines to where they hide to hunt them down and exterminate them.

So it turns out that I was wrong all that time when I assumed that America didn’t need one more man with a gun to protect her from her enemies. We need lots of men (and women) who carry guns, drive tanks, man ships and fly airplanes to keep the rest of us safe.

And I think that today, in contrast to the Vietnam era, we realize the threat is real and the cause is just. Even if you don’t think invading Iraq was the right move for us to make at this time, I think most of us would agree that there will be situations in the coming months and years where we will be forced to send troops to other parts of the world to snuff out developing threats before they can reach us.

I realize now that it takes flesh and blood to defend a country, machines alone can’t do it. The threats are too complex and dynamic. I thank God that we have so many brave men and women who are willing to take on the responsibility of meeting those threats. I also thank Him that one doesn’t stop learning at 18.