This article illustrates the obvious, namely that the U.S. army is stretched too thin.
US Sending 300 Newly Returned Troops Back to Iraq - New York Times
A very -in-the-know active officer who has his hand on the data told me a few months ago that the promotion rate for army captains to be selected for promotion to major is about 95%. Typically, the rate is 60% or so. What this number tells you is that captains, the officers who command companies and fill key staff jobs in battalions and brigades, are leaving the army in droves.