Catch 22. If we stay then we are prolonging the longest lasting armed conflict that we have ever been in. It has been going on almost long enough for children of those who enlisted after the attacks of September 11th 2001 to start enlisting. On the other hand, if we abandon Afghanistan before they have at least a somewhat stable government then we risk seeing it fall back to where it was before. This is partly why Nation Building is such a bad idea anyway.