LONDON — The questions that nobody will ask out loud about the North Atlantic Treaty Organization: How much is enough?

How many new members can NATO afford to take on? If Georgia had already been a member last August, would NATO have gone to war with Russia in its defense? And how far beyond Europe should it try to operate?

When U.S. President Barack Obama asks NATO countries to send more troops to Afghanistan, few member nations will comply, but nobody will ask what a "North Atlantic" alliance is doing in the middle of an Afghan civil war.