The large-scale ground offensive against Islamic State of Iraq and al-Sham (ISIS) to retake Tikrit marks not only a turning point in Iraq's efforts to defeat the extremists within its territory, but a significant milestone for Iran. Iraqi security forces, backed by Iran-supported Shiite militias launched attacks on Tikrit last week. It is the largest Iraqi military operation against ISIS since the militants took over large swaths of Iraq, culminating in their seizure of roughly a third of the country.Qasem Soleimani, the shadowy commander of the Quds Force, an elite branch of the Iranian Revolutionary Guard, reportedly traveled to Iraq to assist in the operation. "While we have to keep an eye on what Iran is doing in terms of its long-term strategy, it's fight against Islamic State serves American interests, and serves the government of Baghdad," Alex Vatanka, a senior fellow at the Middle East Institute, told The Anadolu Agency. The ground offensive, which aims to seize control of former Iraqi dictator Saddam Hussein's hometown of Tikrit, is considered a pivotal step toward retaking control of ISIS's stronghold of Mosul. "This was put together by the Iraqis, formulated by the Iraqis, executed by the Iraqis, and that's the best thing all of us could, frankly, ask for," U.S. Secretary of State John Kerry said last Thursday at a press conference in Riyadh with Saudi Arabian Foreign Minister Saud al-Faisal. "So we take it the way it is and we'll hope for the best results and move from there." But al-Faisal's assessment of the events was in sharp contrast with America's top diplomat. "The situation in Tikrit is a prime example of what we're worried about. Iran is taking over the country," he said in remarks translated from Arabic. The U.S. has assembled a more than 60-nation coalition, which Saudi Arabia is a member of, to combat ISIS in Iraq and Syria.The coalition currently conducts airstrikes against the militants in Iraq and Syria, and trains local forces to take the fight to ISIS. But it has stopped short of sending troops into combat zones to support Iraqi forces something Iran has not been shy about doing. "We will enable their efforts with our air power, with our advice and assistance in any way we can," commander of U.S. Central Command, Gen. Lloyd Austin, told lawmakers during a hearing of the House Armed Services Committee last Tuesday. "But at the end of the day, they have to be able to do this." "I can say that Iran's influence is growing in Iraq, but how much they have, I can't speak to that," he added. Mark Perry, an independent military and foreign affairs analyst who consults at the Pentagon, said Iran is effectively taking the lead in the fight against ISIS, "And the reason it's taking the lead is because Jordan, the United Arab Emirates, Saudi Arabia, and Qatar are not." Pressed on whether Iran's increased military operations in the country concerns him, Defense Secretary Ashton Carter told a hearing of the Senate Armed Services Committee last week, "It does. It does." "I am looking at it with great concern," he said.The top U.S. general, Chairman of the Joint Chiefs of Staff Martin Dempsey, said at the same hearing that though Iran and its allies have been in Iraq since 2004, the offensive "is the most overt conduct of Iranian support in the form of artillery and other things." Still he said that if the forces are able to rid Tikrit of ISIS's forces without inflaming sectarian tensions "then it will, in the main, have been a positive thing in terms of the counter ISIL campaign." David Pollock, the Kauffman Fellow at the Washington Institute for Near East Policy, said that while Iran's actions "definitely" have the potential to stir sectarian tensions, "Right now the Iranians are trying to be careful about not going too far down that road." But even if Tikrit is ridden of ISIS with Iran's and its proxies' support, it will be equally important to ensure that the city's, and indeed the country's, Sunni population does not perceive a potential military victory as being gained at their expense. "You might be able to make progress militarily in a town like Tikrit, but at the end of the day if the broader message to the Sunni population is 'we will marshal massive Shia forces to move in and liberate these towns from ISIS,' what future do the Sunnis see for themselves in Iraq moving forward?" Hardin Lang, a senior fellow at the Center for American Progress, asked, using another abbreviation for the militant group. And though Iran's increased military presence may grant them more political leverage in Iraq for now, it's uncertain how that will translate in the long run. "The United States had 170,000 troops on the ground at one stage, and we couldn't control the political outcome of the country, so it's not clear to me that just because Iran has troops on the ground in the short-term that it is going to give them the influence to call the outcome politically," Lang said.