With the surge in violence in Iraq, one of the main questions is the nature of the key Sunni militant groups in the country, which are widely believed to be behind many of the deadly non-stop bombings.
The main militant group in today's Iraq is the Islamic State of Iraq and ash-Sham or Levant (ISIS/L), which was created in April 2013 by leader Abu Bakr al-Baghdadi as a successor to the Islamic State of Iraq.
Recently, al-Qaeda's central leadership officially denied any link with ISIS on the grounds that ISIS refused Aymen al-Zawahri's order for the nascent group to be disbanded and join forces with the radical Jabaht Al-Nusrah in Syria to topple the regime of Bashar Al-Assad.
However, the narrative of ISIS members and supporters is that the group has been independent of al-Qaeda since the Islamic State of Iraq was announced in late 2006 as an umbrella organization that absorbed al-Qaeda's branch in Iraq.
Although no body claims responsibility for Iraq's suicide bombings, most of the streaks of such deadly attacks against soft targets and civilians in major urban areas - including Baghdad - can be traced to ISIS, though the group's main bases are in the western Anbar and the northern Ninawa provinces. The latter is particularly important to ISIS as a base for financial extortion, where in the city of Mosul, ISIS is the equivalent of a mafia.
However, it is in Anbar where ISIS has tried to show it is building the supposed institutions of an Islamic state - announcing the establishment of an Islamic court in Fallujah, where the militant Islamist group has asserted its control with the backing of disgruntled tribesmen in late December.
Another militant group is Jamaat Ansar al-Islam, which is the successor to the al-Qaeda-affiliated Ansar al-Islam that was disbanded following the US-led invasion.
The group claims attacks primarily in Ninawa, Kirkuk and Salah ad-Din governorates, with occasional operations in the Baghdad area.
Jamaat Ansar al-Islam is a rival to ISIS, despite the fact that both extremist groups share identical al-Qaeda ideology. (especially the ultimate goal of establishing an Islamic state or a Caliphate as well as animosity towards Shiites).
The group's primary grievance against ISIS - echoing that of other rebel groups in Syria- is that ISIS behaves as a 'state' and does not consider itself a group like others, and thus seeks to monopolize control over the insurgency. As a result, Jamaat Ansar al-Islam has clashed with ISIS on multiple occasions in Ninawa and Kirkuk governorates, resulting in dozens of casualties over the past year.
Turning to a more nationalist bent, we mainly find the Naqshbandi Army, which combines Sufi imagery with traditional Iraqi Baathist ideology. Led by Izzat Ibrahim al-Douri (the former Iraqi vice president and army chief until the US-led invasion), the group has an activist wing in the protest group Intifada Ahrar al-Iraq.
More recently, the Naqshbandi Army has been setting up operational fronts across multiple areas -- especially in the eastern Diyala province -- in the form of "Military Councils for the Revolutionaries of the Tribes." Consistent with the Baathist ideology, the group is keen on demonstrating a pan-sectarian appeal.
The relationship between the Naqshbandi Army/its front groups and ISIS is complex. While appreciation may be shown for ISIS' efforts against the Shia-led government, which is viewed by the Naqshbandi as an Iranian 'Safavid' stooge to be overthrown, it is also the case that the groups' agendas are ultimately incompatible, and in many areas, one can hear supporters of one of the two disparage the other.
In short, the Naqshbandi Army appears to offer the main nationalist alternative for Sunnis disaffected with politics. As of now though, no rival groups to ISIS can match the latter's financial capabilities or manpower to constitute a serious terrorist threat for the government, but rather pose a problem for the government in maintaining federal control in Sunni Arab areas.