Common sense, for most of us comes naturally. But for politicians, it seems to be a rare commodity. And it is alarming how little policy seems to reflect it.

Take the president’s Afghanistan policy for instance.  When he made his big announcement in March about the new strategy there, he was warned that setting a withdrawal date certain was a favor to the enemy and would discourage the weaker willed of our allies from continuing to support the mission.

Common sense tells us that if we tell the bad guys when we’re leaving, the bad guys will adapt their tactics to that new information and wait us out.  

Why does common sense tell us that? Because, that’s precisely what we’d do. 

Human nature 1o1. 

If, the US is leaving soon and we are the biggest obstacle to their retaking the country, their obvious new goal is to survive as a effective fighting organization until our withdrawal. Obviously they want to keep the pressure on, but perhaps the big push they were planning this year will now be delayed until the US pulls out. And that seems to be what we see happening there.

Secondly, such a date may have the effect of discouraging allies who were on the fence about staying as a continuing part of the allied effort there. Unfortunately 9/11 seems to have faded in many memories as the true reason for our continued presence in Afghanistan. And, frankly, many of our allies feel they’ve made enough of an effort (and absorbed enough cost) for what was essentially an American tragedy.

But until now, America’s stalwart effort in Afghanistan has basically shamed our NATO allies into staying. The country that has protected Europe for decades has used that leverage and history to maintain the allied effort in Afghanistan. 

Now, however, with the time table for withdrawal announced, all of that’s being recalculated.  As the New York Times reports:

The allies, voicing similar concerns, have abandoned most talk of a conditions-based withdrawal in favor of harder timetables. Britain’s new prime minister, David Cameron, did his best to sound as though he and Mr. Obama were on the same page during his first visit to the White House on Tuesday, but he also told a BBC interviewer while in Washington, “We’re not going to be there in five years’ time.”

The Dutch leave this fall, and the Canadians say they intend to follow suit by the end of 2011.

As one of Mr. Obama’s top strategists said this week, with some understatement, “There are signs that the durability of this mission has to be attended to.”

That’s common sense coming to the fore – at least among our erstwhile allies. The thinking, again not at all difficult to anticipate, says that if the US is going to withdraw by next year, there’s certainly no reason for us to continue the mission. And, consequently, they’ve chosen to interpret the date given by Obama as more hard and fast date instead of the “conditions based” date Sec. of Defense Robert Gates insists it is. 

Last, but certainly not least, common sense tells us that setting a withdrawal date certain gives political opponents to our continued presence there new ammunition. Sure enough:

Mr. Obama has begun losing critical political figures and strategists who are increasingly vocal in arguing that the benefits of continuing on the current course for at least another year, and probably longer, are greatly outweighed by the escalating price.

In this case political common sense (a version of common sense politicians do have which finds their fingers permanently in the wind sensing any subtle shift in the political air currents) comes into play. If we’re leaving in a year, it makes perfect sense to a) start expressing concern about the progress of the war (so they can be on the “I told you so side” when we pull out without obvious success) and b) start seriously grousing about the cost of the war.

Both of those things are now increasingly happening. What was the “good war” when Mr. Obama was running for President is now slow walking into the second Vietnam. And if ever a comparison to that war is apt, this is it. Once we announced our withdrawal date certain in Vietnam, the North Vietnamese simply laid back, kept a modicum of pressure on and essentially waited, until we left before launching huge attacks in the South.

That, unfortunately, is exactly the scenario that seems to be playing out here. You can’t help but wish that politicians, especially those touted as being so “intelligent,” had two things they seem to never have – common sense and an understanding of history. 

Instead, we get politics, nuance and decisions so lacking in common sense that seem likely to lead to disaster.