MechAg94 - the Democrats haven't "defunded the entire DOD." The situation, as I understand it, is that Bush refuses to sign any spending bill which does what you specify, eliminate funding for Iraq. And there aren't enough Republicans willing to break ranks to override the veto.
(last paragraph of the AP story - The Democratic-led House has passed a $50 billion war spending bill that would keep operations going for several more months, but it sets a goal of bringing most troops home by December 2008. President Bush threatened to veto it, and the measure was blocked in the Senate.)
It's like the writers in CA/NY - they aren't, really, 'on strike.' Their contract expired and they refuse to go back to work under the old terms.
A credible threat of impeachment would produce prompt results.
No, it wouldn't. They might, if lightning struck, manage to 'impeach' Bush - but there is simply no way that enough Republicans cross over to remove either Bush or Cheney (assuming you got every Democrat on board).
Impeachment is a pipe dream and even considering it works counter to any reasonable effort to end the debacle.