April 12: Tikrit next target
April 11: Saddam 'no longer in power'
April 10: Advance on northern Iraq
April 9: Regime loses grip on Baghdad
April 8: Tightening grip on Baghdad
April 7: Airstrikes target senior officials
April 6: Baghdad surrounded
week of March 31
April 5: U.S. forces enter Baghdad
April 4: Republican Guard regroup
April 3: Ground troops clash at airport
April 2: Helicopter down in Iraq
April 1: Marines fight Republican Guard
March 31: U.S.: Some Iraqi forces halved