The Shia cleric Muqtada al-Sadr, commander of the Mahdi Army militia responsible for the killing and wounding of thousands of US and UK personnel, Iraqi state forces, rival militias and civilians, has returned to Iraq having spent at least three-years of self-imposed exile in Iran, where he has pursued religious studies.

His return, not necessarily the first since he left in 2007 but certainly the first to be made public, is arguably telling of the changing dynamics of the Iraqi political arena and indeed of the Sadrist movement itself.

The Sadrists won nearly forty seats in last year’s parliamentary elections. With seven ministries to his bloc’s name and the deputy-speaker of parliament post, as well as a collection of governorships in the south of the country, al-Sadr’s return may have also been part of this package of concessions offered to him by arch-enemy Prime Minister Nouri al-Maliki, in return for his backing of Maliki as premier. This is since the cleric still has an outstanding arrest warrant against him for the murder of Sayyid Abdul-Majid Khoei in 2003, one of Iraq’s leading Shia clerics backed by both the US and UK.

That warrant may soon be revoked and al-Sadr’s return, if permanent, is likely to be part of a long-term strategy to embolden his bloc and its orbit of influence in the country.

His return will consolidate his movement’s political gains and will galvanise his supporters, numbering millions of Shias and derived predominantly from the impoverished Baghdad suburb of Sadr City. This becomes particularly crucial for the movement as a result of internal divisions it has suffered in recent years. The most notable group to splinter from the movement is the so-called League of the Righteousness, led by Qais al-Khazali, the militiaman complicit in the 2007 kidnapping of Britain’s Peter Moore. (The League of the Righteousness was recently involved in a gun battle with the Sadrists).

Al-Sadr’s return could also be part of a broader, longer-term plan to place himself as the successor to Grand Ayatollah Sistani, Iraq’s leading Shia cleric and the spiritual leader of Shia Muslims around the world. Al-Sadr, who himself comes from a famous clerical family has for long competed with Sistani for power and influence.

However, that will depend on the state of al-Sadr’s religious credentials. It takes decades to reach the rank of Grand Ayatollah. More importantly will be relations between al-Sadr and other leading figures of the clergy in the holy city of Najaf. Al-Sadr faces competition from Ayatollah Mohammad Saeed al-Hakim to become Sistani’s successor. Al-Hakim is widely tipped to be the successor; but what could make the competition for clerical authority violently uncertain is the fact that al-Hakim is more hostile to al-Sadr than Sistani is and, significantly, has not hesitated to outspokenly and publicly criticise him.

For now, it will be a case of waiting and seeing. Al-Sadr's speech today will be closely assessed to determine his long-term plans and his position on the many issues facing Iraq, including the future of the fragile government the country now has and the US withdrawal at the end of this year. It is not yet certain al-Sadr will stay in Iraq. He may return to Iran and continue his religious studies, lest the suggestion that he left Iraq because he feared for his life or because of the arrest warrant issued against him is given credence.

It also remains to be seen whether Iraq is big enough a place for both al-Sadr and al-Maliki, who went head-to-head in the 2008 Battle for Basra that ultimately led to defeat and a dramatic decline in power for the former. Al-Sadr’s return had to have been approved by Iran and it came on the same day Iranian foreign minister Ali Akbar Salehi visited Baghdad. Iran may have sanctioned al-Sadr’s return to put a check on Maliki, who has in the past moved against Iranian interests in Iraq.

There is further uncertainty about what implications al-Sadr’s arrival may have for the US, as it prepares to withdraw completely by the end of this year. The US will be ill at ease with the arrival of what it regards as an Iranian proxy so close to its departure. During his visit, the Iranian foreign minister repeated Iran's demand that Maliki's government not extend the US troop presence. Al-Sadr's return may be an attempt to ensure just that.