Question: What happens when other major powers face growing security problems, and begin to wonder whether the United States will continue to protect them? 

Answer: They stop free-riding quite so much and start doing more themselves.

Case in point: Japan. As the New York Times reports today, Japan has responded to fears of a rising China, potential dangers from North Korea, and concerns about the U.S. commitment to Asia not by "bandwagoning" with China or opting for neutrality, but by bolstering its own defenses and reaffirming its security ties with America.  Its goal, according to the Times, is to become a "full military partner" with the United States.

There are two obvious, lessons to be drawn from this example. The first is that the United States can take advantage of the tendency of great powers to balance to reduce some of its own defense burdens, confident that wealthy allies like Japan can take up some of the slack. By playing "hard to get," in other words, we can "pass the buck" to our allies to a greater extent than we have in recent decades. The United States can do this in part because it has the luxury of being safe and secure in the Western hemisphere while our allies lie closer to potential sources of danger, and smart strategists should take advantage of this favorable situation. If the United States insists on doing it all, of course, we can confidently expect other states to keep free-riding on our efforts.

The second lesson, however, is that there's a limit to how far one can pass the buck to others.  If the United States were to withdraw entirely from Asia, or to reduce its military capabilities too much, then some other states might eventually decide to make other strategic arrangements. But given that the U.S. is spending nearly 5 percent of GDP on national security these days, while Japan spends less than 1 percent, I'd say we've have a long way to go before our allies think seriously about realigning.  

Remember: The main reason for a state to have allies is so that they can help make it more secure. If having a large array of allies just means the United States has more areas it is obligated to defend, then maybe we need to rethink how many of those commitments actually enhance our security, and how many of them just add burdens without compensating benefits.

Whatever numbers you hear about the cost of Obama's escalation in Afghanistan are bound to be low. Once you add in veterans' benefits, the long-term costs of medical treatment for wounded soldiers, replacement costs for the equipment they will use up and wear out, etc., you end up with a lot more than the extra $30 billion that Obama mentioned in his speech on Tuesday. If you want to be prudent, assume that the true costs are at least twice what you've heard. Together with the money already allocated, it's going to be well in excess of $100 billion per year. Keep that in mind the next time you pass a rusting bridge, or when your local School Board has to cut its budget and lay off a few more teachers.

But there is another cost to digging in deeper in Afghanistan. Obama has now bet the future of his presidency on being able to achieve something he can describe as "success" there, and he has only 18 months to do it. He's shackled with a sluggish economy that is unlikely to turn around soon, so there are going to be plenty of disaffected voters by 2012. The Dems are going to lose a bunch of seats in the midterms, making it even tougher to pass domestic legislation that might win broad voter approval. And having alienated a lot of the people who worked their butts off for him in 2008 (because they thought he would be different), he's going to have a hard time generating the sort of grass roots enthusiasm that won him the White House in the first place. Progressive Dems won't switch sides, but some of them will stay home. He may even have trouble getting Shepard Fairey's endorsement if Afghanistan doesn't turn around fast.

All this means that Obama will have to devote a lot of time and attention and political capital to the war in Afghanistan, an impoverished land-locked country of modest strategic importance. Meanwhile, life will go on in the rest of the world, and U.S. relations with a number of far more important countries will not receive the attention they should. Here are three examples.  

1. The new Japanese government is actively rethinking its security partnership with the United States, and while I don't think we should rush to accommodate all of their concerns, we certainly ought to be paying very close attention. But having just returned from a quick Asian trip, Obama is likely to put relations with Japan (and other key Asian allies) on the back burner. That would be a mistake, because a significant erosion in the U.S. position there would have far more significant effects than the outcome of the Afghan campaign. Mapping out a long-term security strategy for Asia will take time and attention, and that's precisely what Obama doesn't have right now.

2. The democratic government of Turkey has been carving out a more independent and influential position at the crossroad of Europe and Asia.  Its recent decision to reject Israeli participation in a scheduled NATO military exercise (which led to the exercise being canceled) is one sign of this new independence, as is its more active engagement with Syria and Iran. This development is not necessarily a bad thing, if Turkey uses its growing influence constructively. But it is a new feature of the global scene that calls for sustained attention and a nuanced U.S. response, and I'll bet it doesn't get either.

3. Brazil is becoming a more independent and less deferential power here in the Western hemisphere. President Lula da Silva has opened more than 30 embassies around the world since 2003, remains on good terms with Venezualan strongman Hugo Chavez, has defended Iran's nuclear research program, and recently hosted Iranian president Mahmoud Ahmadinejad in Brasilia. Obama and Lula have exchanged letters on some of these issues, and Brasilian Foreign Minister Celso Amorim has said there is "no crisis" between the two countries. But he has also said that the two countries "are in different latitudes" and "must get used to disagreeing." A stronger and more assertive Brazil will also create new diplomatic opportunities for other Latin American countries (who have long resented U.S. dominance in the Western hemisphere), as well as opportunities for other great powers. And might this herald a gradual erosion of the Monroe Doctrine?

None of the developments poses an immediate threat to vital U.S. interests, but all could use some adroit attention on Washington's part and a sophisticated strategy for dealing with them. But my guess is that they will get short shrift, because Obama's attention and a lot of the intellectual oxygen in Washington will be sucked up by the endless debate on AfPak.

You might reply that I'm being too pessimistic, because Obama has a talented administration that is deep in foreign policy expertise and nobody expects the President to do everything himself. He can turn these problems over to DoD, the NSC staff, and the State Department while he focuses laser-like on Central Asia (and the economy).

I wish I could believe that, but I haven't seen much evidence of a smoothly running foreign policy apparatus so far. What I read suggests that the White House holds tight control on the main lines of policy, and apart from the president himself (who does show occasional flashes of strategic vision), I still can't figure out who's in charge of the big picture. So in addition to the human and financial costs of the decision to escalate in Afghanistan, throw in the opportunity costs. There are only 24 hours in a day and seven days in a week, and a lot of important issues are going to get less attention than they deserve.

MANPREET ROMANA/AFP/Getty Images