SADLER: I can tell you since we've come back to Erbil, we now have confirmed reports from embedded correspondents on the ground that the U.S. Marine Corps have begun engaging Iraqi resistance in and around Tikrit. EDITOR'S NOTE: CNN's policy is to not report information that puts operational security at risk.

DoD: Without the spectrum, the Iraqis could not mount a coordinated offense and could not sustain any defense. Remember that the electromagnetic spectrum hold[s] the key to our successful use of our technological advantages of today and tomorrow.