Iranian role in Iraq offensive to recapture Tikrit?

Iraq has launched a military operation to recapture Tikrit, the hometown of former leader Saddam Hussein, from Islamic State (IS) and its allies.

A force of about 30,000 troops and militia were said to be attacking on different fronts, backed by air strikes from Iraqi fighter jets.

Meanwhile, a Shia militia commander has told the BBC that Iran's Gen Qasem Soleimani is also taking part in the operation.

The BBC's Paul Adams has this analysis of Iran's role in the conflict.