About 30,000 members of Iraq’s military and militias are participating in the offensive against Islamic State fighters in the militant group’s stronghold of Tikrit, Agence France-Presse reported. The force targeted jihadist positions in and around the Iraqi city Monday after launching the large-scale offensive to reclaim northern and western Iraq from the group.

"Security forces are advancing on three main fronts towards Tikrit, Ad-Dawr (to the south) and Al-Alam (to the north)," a senior army officer involved in the operation told AFP. "The attack is being carried out using fighter jets, helicopters and artillery targeting Tikrit to secure the advance and cut supply routes."

The offensive was announced by Iraqi state television a day after Prime Minister Haider al-Abadi visited troops stationed on Tikrit’s outskirts and made a speech in which he declared that the “zero hour” for Tikrit’s liberation was near, the New York Times reported. The prime minister also promised amnesty to local residents who had been forced to join the Islamic State, also known as ISIS, but said that they had a “last chance” to lay down their weapons and assist the government’s effort to stamp out the militant group from the area.

If the offensive in Tikrit is successful, it would mark the biggest victory yet in Iraq’s battle against ISIS, which gained control of significant swathes of the country last summer. Tikrit is the hometown of deposed Iraqi dictator Saddam Hussein, who was toppled by the 2003 U.S.-led invasion of Iraq, and is symbolically valuable in the battle against ISIS, according to the Associated Press. The group was able to rally Sunni support in the country by portraying its advance as a revolt against the Shiite-led government ahead of its capture of Tikrit in June.

While capturing Tikrit would mark a major victory for the Iraqi military and the U.S.-led coalition effort against ISIS, it might also impact the campaign to re-capture Mosul, Iraq’s second largest city and the militant group’s major Iraqi hub, the AP reported. ISIS still controls much of the western Anbar province and would likely be able to mount attacks against government forces stationed in Tikrit, potentially diverting much-needed forces from an eventual offensive against Mosul.