There were conflicting reports as to just how much headway the Iraqi military made in its initial thrust toward Tikrit, the hometown of Saddam Hussein.
Residents said militants were still in control of the city by nightfall, while Iraqi officials said the troops had reached the outskirts and even entered Tikrit itself.
What was clear, however, was the government's desire to portray the campaign as a significant step forward after two weeks of demoralising defeats at the hands of insurgents led by the al-Qaeda breakaway Islamic State of Iraq and the Levant.
Iraq's large, US-trained and equipped military melted away in the face of the militant onslaught, sapping morale and public confidence in its ability to stem the tide, let alone claw back lost turf.
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The Tikrit operation, if successful, could help restore a degree of faith in the security forces, as well as embattled Prime Minister Nouri al-Maliki.
Today's fighting began before dawn with helicopter gunships carrying out airstrikes on insurgents who were attacking troops at a university campus on Tikrit's northern outskirts, Iraqi military spokesman Lt General Qassim al-Moussawi said.
Sporadic clashes continued throughout the day at the university. At the same time, several columns of troops pushed north toward Tikrit from Samarra, a city along the banks of the Tigris River and home to an important Shiite shrine, a senior security official said on condition of anonymity because he was not authorised to brief the media.
By sundown, Lt General Ahmed Abu Ragheef, a commander in the Salahuddin Operational Command, said a column of troops had reached the edge of Tikrit, while another had secured an air base that previously served as a US military facility known as Camp Speicher.