Why is Iraq so important to Iran?
General Qassem Soleimani has long cast a shadow over the foreign policy of Iran. His role goes far futher than his rank. As head of the Al Quds force, he's responsible for secret military operations outside of Iran. He is also a skilled political operator.
To call him a warrior diplomat would be an understatement. He is, in many ways, the Iranian influence abroad.
Rumours have circulated that he is here in Iraq to deal with the country's battle against Sunni rebel groups and the Islamic state of Iraq and the Levant. One foreign diplomat told me he is in Baghdad with a number of advisers and is helping shape strategy.
Iraq is hugely important to Iran. The majority of Iraq's population are Shia Muslim, as is Iran. Iraq is also home to the holy cities of Najaf and Kerbala, and to the Askari shrine. These sites are important to all Muslims, but for the Islamic Republic of Iran they represent the very heart of Shia history.
Iran has long supported the Iraqi government of Nouri al-Maliki.
The Iranian president, Hassan Rouhani has reaffirmed this is a number of statements, and promised to defend the holy cities.
For all these reasons and more, the involvement of Soleimani shouldn't come as a surprise. He has built relationships here in the years since the US invasion of Iraq in 2003 and has the ear of the government and the military.
He is a very busy man. His recent assignments have had him in Syria, with Hezbollah in Lebanon and of course here in Iraq.
Mahjoob Zweiri, a professor of contemporary Middle Eastern history at the University of Qatar and an expert on Iran, tells me that Iran's involvement is both practical and ideological.
"There was no indication that this crisis would arise on this scale, so there was no plan to deal with it," he said. "Iran is trying to manage the crisis. It already has a bigger crisis in Syria and this one must be handled carefully so as not to escalate."
That sense of escalation is concerning to many. In 2006 al-Qeada attacked the Askari shrine in the northern city of Samarra. It plunged the country into a sectarian war that almost spilt it, and its repurcussions are still felt today.
The ISIL have promised to attack the Shia shrines and holy cities, a position that puts them at odds with Sunni allies who have said they will protect the sites.
Preventing another attack on the shrine, and indeed violence in Najaf and Kerbala, is crucial if Iraq is to survive this crisis. Soleimani is not doubt aware of this.
Iranian involvement in Iraq has been complicated. It's alleged to have supported groups like the Islamic State of Iraq, a precursor to ISIL, in the early days of the US invasion of Iraq.
Over the last 30 years there has been little trust between Iran and the US. Defending Iranian territory has meant the Islamic Republic has made unusual alliances, particularly with US troops on two neighbouring countries, Iraq and Afghanistan.
Those alliances could prove crucial in the coming months, says Mahjoob Zweiri. "Iran's knowledge of groups like the Islamic State of Iraq means that they're in a good position to be able to advise on the fightback, and that'll be valuable to the Iraqi government."
But they won't do this loudly. Iran will play a very quiet role in this conflict. It will want to let the Iraqi government take the credit for any successes it might have against ISIL and its Sunni allies.
Talking the talk
However in recent days we've heard a lot from various sources that Iran and the US are talking with each other about Iraq but mindful of domestic politics the US is dialling back comments made by senior politicians, such as the secretary of state, John Kerry, about cooperation.
For Iran, however, keeping things quiet and working behind the scenes has always been their way. A lack of trust between Iran and the West means that is unlikely to change.
As one western diplomat told me: "They don't trust us, so why would they back us publicly? They, like us, have a domestic audience that they need to manage and with relations so fragile, why shout? It's better for them to keep things quiet and work in the background. If things go wrong, they have plausible deniability."
Denial or not, Iran is a key player in this conflict and it alongside Turkey and Saudi Arabia will be competing for its own interest. To that end, a man like General Qassem Soleimani is crucial for his country.
He and his advisers will be quietly moulding and finessing Iran's strategy in Iraq - a strategy that may put them on the same side as the US, and one that we will see being played out over the coming months.
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