As Iraqi and Shia militias try to recapture the city of Tikrit from Islamic State (IS), the key role of Iran in the campaign is becoming clearer.
Shia militia sources in Iraq have confirmed that Gen Qasem Soleimani, the commander of the Iran's Islamic Revolution Guards Corps (IRGC) Quds Force is personally taking part in leading the operation.
Tikrit, 150km (95 miles) north of Baghdad, has been occupied by IS for more than eight months and an offensive to recapture it was declared by Iraqi Prime Minister Haider al-Abadi on Sunday.
The Iraqi army and security forces along with Shia militia groups who call themselves Popular Mobilisation units are pushing into Tikrit from several directions.
As sources on the ground have told BBC Persian, a number of IRGC officers were involved at a command level before the operation was officially launched.
Iranian authorities are yet to comment officially but Iran's Fars news agency, considered to be very close to the Revolutionary Guards, has extensively reported on the role of Gen Soleimani in the operation.
It has even published photographs that show the general among Iraqi commanders and officials, saying they were taken around Tikrit.
One of the groups in the Popular Mobilisation units is Saraya al-Khorasani (Khorasani Brigades), who say they are under the command of Iran's Supreme Leader Ayatollah Ali Khamenei.
A Brigades commander told BBC Persian that Iranian forces under Gen Soleimani were training and morally preparing Iraqi Shia fighters for the operation long before it began.
Although Iran was left out by the US and its allies when they formed a coalition against IS last year, its direct involvement in fighting IS militants in Iraq was revealed long before the coalition was formed.
Since last summer, a number of Shia militia groups have emerged in Iraq that openly pledge their allegiance to Iran and declare themselves as followers of Ayatollah Ali Khamenei.
Iranian officials have always pointed out that their country is helping both Shia and Kurdish forces in the fight against IS but it was in a battle in late August 2014 that Iran's direct military involvement was made clear.
Back then, Iranian forces were playing an openly active role in helping Kurdish and Shia forces take back the town of Amerli from IS in a joint operation.
It was during the battle of Amerli that BBC Persian accessed the weapons and ammunitions sent from Iran for the militia forces.
Gen Soleimani's has been the recognisable face of Iran's influence and involvement in Iraq since the fight against IS began.
Now, if the operation to liberate Tikrit leads to success then it will mark a victory for Iran and its man in the field who may add to his titles, the conqueror of the home town of his old enemy, former Iraqi leader Saddam Hussein.