It's not a purge. It's a direct result of today's Obamaconomy. People who would've normally gotten out after their time was up are re-enlisting because there isn't much in the civilian world with the pay and bennies we're getting in the military. Combine this with drawdowns and there's little choice but to give service members of all ranks pink slips.
We went through this in the Navy a couple years back and it has been devastating to our manpower. We have the same missions to do and far less assets to do them with.
Hang Tough, Drew!
Clinton did the same thing. It was only after 9/11 that people realized how exposed we were and began building the military back up.
Fortunately, what saved us last time was the ability to use technology to make our military more efficient and effective.