Shiite fighters fire a rocket during clashes with Islamic State militants in Salahuddin province, Iraq, on Tuesday. Thousands of Iraqi soldiers and Shiite militiamen sought to seal off Islamic State fighters in Tikrit and nearby towns. (REUTERS/Ahmed Al-Hussaini)

The assault on the Islamic State in the Iraqi city of Tikrit began Monday, a massive operation involving some 30,000 Iraqi troops and Shiite militiamen, some of them backed by the Iranian government. It’s already been a bloody fight, and it could take days: The militants have spread bombs throughout the region to slow the assault, hindering efforts to take back a city of more than 250,000 people.

Here’s a look at the battle through photographs released so far. They show a broad array of military equipment and weapons being used. Some of the arms have been bought or supplied by the United States, although the Americans have continued to sit out the battle.

The city
Tikrit was home to Saddam Hussein, who was hanged in 2006 after being convicted of war crimes. It has a population of about 250,000 people, and at least 28,000 of them have fled the area, according to the United Nations.

A picture taken from the village of Awja, on the outskirts of the Tikrit, on Thursday shows the palace of Iraq’s former leader, Saddam Hussein.  (AFP PHOTO / AHMAD AL-RUBAYEAHMAD AL-RUBAYE/AFP/Getty Images)

A picture taken from the village of Awja shows a general view of the city. (AHMAD AL-RUBAYEAHMAD AL-RUBAYE/AFP/Getty Images)

The combined force
The force attempting to take back Tikrit massed outside the area, and has pressed in from several directions. It includes Iraqi troops and several kind of Shiite militias. The involvement of the militias has raised concerns about sectarian violence, since Tikrit primarily a Sunni city.

Iraqi soldiers on duty at a military barracks in Alam town, south of Tikrit city. (EPA/STR)

Volunteers from an Iraqi Shiite militia take up a position near Tikrit on Monday. (EPA/STR)

Iraqi security forces and volunteer Shiite fighters gather in the city of Samarra on Thursday ahead of moving north into the city of Tikrit. (AHMAD AL-RUBAYEAHMAD AL-RUBAYE/AFP/Getty Images)

Weapons and equipment
The assault has included the use of tanks, armored personnel carriers, helicopters, rockets and mortars, along with a variety of small arms. Some of it — like Black Hawk helicopters — is American-made.

Iraqi security forces and Shiite fighters clash with Islamic State militants in Salahuddin province on Monday. (REUTERS/Thaier Al-Sudani)

A member of the Popular Mobilization unit, a Shiite militia, takes position in the village of Awja. (AHMAD AL-RUBAYEAHMAD AL-RUBAYE/AFP/Getty Images)

A Shiite fighter carries a rocket-propelled grenade launcher as he walks ahead of a tank in the town of Hamrin in Salahuddin province. (REUTERS/Stringer)

An Iraqi air force helicopter fires a rocket toward Islamic State militants during heavy fighting in Salahuddin province on Wednesdsay. (REUTERS/ Mahmoud Raouf)

Shiite fighters load rockets into a launcher during heavy fighting against Islamic State militants in Salahuddin province on Wednesday. (REUTERS/ Mahmoud Raouf)