The battle for Tikrit

Smoke rises during fighting between the Iraqi army and Islamic State militants, in Tikrit on Tuesday.  (STR / EPA)

A member of Iraqi security forces plants the national flag as they surround Tikrit during clashes to regain the city from Islamic State militants on Monday.  (Khalid Mohammed / Associated Press)

Iraqi security forces attack Islamic State extremists in the streets of Tikrit on Monday.  (Khalid Mohammed / Associated Press)

Iraqi security forces launch a rocket against Islamic State positions during clashes in Tikrit on Monday.  (Khalid Mohammed / Associated Press)

Iraqi security forces search house to house looking for fighters of Islamic State in Tikrit on Monday.  (Khalid Mohammed / Associated Press)

An Iraqi soldier searches for fighters of Islamic State group in Tikrit on Monday.  (Khalid Mohammed / Associated Press)

An Iraqi soldier fires during clashes to regain the city of Tikrit on Monday.  (Khalid Mohammed / Associated Press)

Iraqi security forces launch rockets against Islamic State positions in Tikrit on Saturday.  (Khalid Mohammed / Associated Press)

Iraqi security forces patrol in Tikrit. Rockets and mortar rounds echoed across the hometown of former strongman Saddam Hussein on March 12.  (Khalid Mohammed / Associated Press)

Shiite militiamen take combat positions in Tikrit.  (Khalid Mohammed / Associated Press)

Iraqi security forces and allied militiamen prepare to attack Islamic State extremists at Camp Speicher, the front line in Tikrit.  (Khalid Mohammed / Associated Press)

Iraqi army armored vehicles move into position to attack Islamic State extremists in Tikrit.  (Khalid Mohammed / Associated Press)

Iraqi Defense Minister Khaled Obeidi, seated, confers with an officer during operations against Islamic State militants in Tikrit.  (Khalid Mohammed / Associated Press)

Iraqi security forces and allied Shiite militiamen prepare to attack Islamic State extremists in Tikrit.  (Khalid Mohammed / Associated Press)

Pro-government militiamen take part in a military operation to take control of Tikrit from Islamic State militants on March 11.  (Ahmad Al-Rubaye / AFP/Getty Images)

Iraqi medics treat wounded fighters at a field hospital during a military operation to retake control of Tikrit.  (Ahmad Al-Rubaye / AFP/Getty Images)

Iraqi government forces deploy during an operation on March 11 to regain control of Tikrit, north of Baghdad.  (Ahmad Al-Rubaye / AFP/Getty Images)

Mourners chant slogans against Islamic State during the March 11 funeral procession for three members of a Shiite group killed in Tikrit while fighting Islamic State militants.  (Jaber al-Helo / Associated Press)

Pro-government Iraqi militiamen wait to take part in a military operation on March 11 to take control of Tikrit.  (Ahmad Al-Rubaye / AFP/Getty Images)

Iraqi government forces battle for control of Tikrit against Islamic State militants on March 11.  (Ahmad Al-Rubaye / AFP/Getty Images)

Iraqi Lt. Gen. Abdul-Wahab Saadi, second from right, inspects government forces on the outskirts of Tikrit as they prepare to launch a military operation against Islamic State fighters on March 11.  (Ahmad Al-Rubaye / AFP/Getty Images)

A pro-Iraqi government fighter prepares to advance toward the center of Tikrit on March 11.  (Ahmad Al-Rubaye / AFP/Getty Images)