(CNN)There is only one likely outcome for Baghdad's current military offensive to reclaim Tikrit: defeat for ISIS. The campaign to restore central government authority over the restive Salahudin province is seen as both symbolic and strategic for Baghdad which has invested too much already for it to afford losing this battle. ISIS are said to have booby-trapped much of the city in an attempt to slow down the government assault. However, the task at hand has been made easier for Baghdad given that most civilians in Tikrit have already fled -- both to Kurdistan in the north as well as south to Baghdad -- leaving behind mostly ISIS jihadists who defend the city, according to Iraqi constitutional specialist Zaid al-Ali, who is from the city. Initial reports of the multi-pronged attack on Tikrit have been encouraging. Iraqi forces have already cleared a number of areas on the outskirts and are expected to continue advancing towards the city center as both heavy artillery and helicopter gunships pound ISIS militants who have taken up defensive positions. Another crucial element for the success of this battle will be the varied make-up of the groups involved in the fight. The joint Iraqi forces fighting to retake Tikrit include Iraqi troops, members of the mainly Shia Hashd al-Shabi paramilitary force, members of the Sunni Sons of Salahuddin brigades, and other Sunni tribal fighters. The offensive involves around 30,000 fighters in all. Although the campaign is Iraqi-led, help from outside is also going to play an important role. Though the United States has not conducted any airstrikes in this campaign yet, this may well change as the battle develops. Iran, in stark contrast to the U.S., provided Iraq with immediate and much-needed military assistance when the security crisis escalated last June. The Iranians are heavily invested in this current campaign and are also not going to let the Iraqis lose. Unlike in Syria, the Americans and Iranians both share a common enemy and a common friend in Iraq, but due to wider political considerations neither Washington nor Tehran will admit that there is any form of tacit cooperation in Iraq. However, the campaign for Tikrit is just another front where such cooperation is likely to be already happening behind the scenes. Baghdad will make use of U.S. intelligence that will almost certainly be shared with the Iranian officers who are advising the Iraqi army. General Qasim Suleimani, the commander of the Iranian Revolutionary Guard Quds Force, who has played a key role in the fight against ISIS, was reported to be near Tikrit just hours after the military campaign was officially launched. Iran provides military advice, support and weapons not just through the central government in Baghdad but also directly to a number of increasingly powerful Shia militia groups that now operate under the state-sponsored paramilitary committee, the Hashd Al-Shabi, known as the "Popular Mobilization Units." The two key Iraqi leaders of this paramilitary command, Hadi al-Ameri and Abu Mehdi al-Mohandis, were also pictured together with General Fadhil Barwari, the commander of Iraq's elite Special Operation Forces. Though there are few civilians left in Tikrit, all eyes will be on the Iraqi security forces -- and especially the Shia militias --- to see if abuses are carried out once the enemy is routed. Prime Minister Abadi already warned the anti-ISIS fighters to protect civilians and properties in the area and also gave the "misled" ISIS militants a last chance to lay down their arms before the troops made their advance. The battle is an especially emotional one for the Shia soldiers and fighters as Tikrit is the site of the Camp Speicher massacre last June, where 1,700 Shia soldiers were captured, separated from their Sunni comrades and then summarily executed in an atrocity that was documented by ISIS as a powerful propaganda film. However, it is encouraging that both Shia and Sunni fighters are supporting the army in its effort to defeat ISIS. The cooperation between Shia and Sunni fighters will be crucial not just in the ongoing offensive in Tikrit but will also set the stage for further cooperation in the strategic campaign to recapture Mosul. Politically, these groups may not see eye-to-eye and of course there remain deep ethno-sectarian tensions in Iraq and beyond, but regardless of these differences they all view ISIS as a common threat and enemy that must be defeated. To be sure, the Sunni tribesmen involved in this campaign are more anti-ISIS than they are pro-government, but that they can work with the pro-government Shia militias is both good news and good progress for a country believed to be ripping itself apart along ethno-sectarian lines.
Likely outcome for Baghdad's current offensive to reclaim Tikrit is defeat for ISIS, writes Hayder al-Khoei . Al-Khoei: Crucial element for success will be varied make-up of the groups involved in the fight . Both Shia and Sunni groups view ISIS as a common threat and enemy that must be defeated, he adds .