For Western military analysts and policy-makers trying to unravel the implosion of Iraq, a Marxist analysis of the situation is long overdue.
The appeal of Isis's extreme religious doctrine to Sunni Arab Iraqis has been well documented, but in fact it is the economic situation of many of those Sunni Arab civilians that lies at the root of their support for the insurgents.
As Isis has overrun great swathes of Iraq in the past two months, it has frequently received complicity, if not all-out support, from many Arab Sunnis (I focus here only on Arab Sunnis; Kurdish Sunnis have met Isis with profound hostility and resistance).
While US analysts believe that Isis comprises only around 10,000 fighters, it has swept with relative ease through the north and west of the country thanks to the Sunni-dominated communities that live there, which have extended a sympathetic reception to the insurgents.
On a superficial level, the attraction of Isis to Iraq's Sunni Arab underdogs is obvious: here is a group of the same sect of Islam that promises them preferential treatment in society and better opportunities than they could ever hope for under the current Shia-dominated leadership.
After all, the plight of the nation’s Sunnis, disenfranchised under Nouri al-Maliki’s Shia-dominated government, is well known.
The religious objectives laid out by Isis are also attractive to Iraqi Sunnis. The insurgents' extreme violence is framed as religious cleansing – wiping out the Shia imams and believers from the holy cities of Najaf and Karbala.
As the New York Times has noted: "Mass execution has been meshed with the use of religious symbolism by the insurgents".
And while Isis's insistence on adherence to extreme conservative conventions may appear harsh to outsiders, the clarity and simplicity of Sharia law is always going to appeal most to downtrodden and insecure communities, like Iraq's poorer Arab Sunnis, who tend to prefer robust law and order to instability.
In addition to the ideological appeal of Isis, the group's social constitution has been a boon in winning over rural Sunnis. There is, relatively speaking, a flat structure to Isis's social and religious make-up that appeals to a poor, agragian society in a way the hierarchical, class-based Sunni Islam of Saudi Arabia never would.
Above all, however, it behoves to consider the specific economic circumstances in which many Iraqi Arab Sunnis have found themselves – roundly ignored by most analysts – in order to explain their inclination to embrace the militants.
Economic deprivation has plagued the Iraqi Sunnis, who are thought to comprise between 20 and 35 per cent of the population (accurate data is lacking), since the 2003 war.
Driven from power by Western forces after enjoying supremacy, and comprising the majority of Saddam's Ba'athist government (Saddam himself was a Sunni Arab from Tikrit), the Sunnis have been increasingly marginalised in the past ten years.
Shunned from the Shia-dominated security forces, Sunnis have little stake in the defense of the country. More than that, however, al-Maliki's refusal to incorporate the Awakening squads of Sunni fighters, who supported the deposition of Saddam and aided the West's invasion, into the mainstream security forces, has meant that most of these Sunni Arabs been faced with a limited choice: suffer unemployment, or join Isis.
While residual Sunni neighbourhoods remain in Baghdad, and the city of Mosul in the north is still a hub of metropolitan Sunnis, around half the country's Sunni Arabs are agragrian, rural-dwelling people.
Despite that, they have been hit hardest by the series of poor harvests and food shortages that Iraq has suffered in the past decade.
It is a bitter irony that Iraq, part of the fertile crescent in the Middle East that has been farmed for 8,000 years, and irrigated by not one, but two great Asian rivers, the Tigris and the Euphrates, has suffered severe agricultural decline.
Years of neglect and conflict advanced the contraction of the sector in the decades before the Iraq invasion, but agricultural productivity declined a devastating 90 per cent after the 2003 war.
According to reports, Iraqi agriculture is in crisis. The misery of rural Sunni communities that rely on agriculture for their income and subsistence, was compounded by six years of the driest winters on in Iraq from 2004 onwards.
Once a major exporter, Iraq is now reliant year-round on food imports. Many Sunnis have been working hard on the land, and yet struggling to eat, while perceiving metropolitan Shias in Baghdad and the east to be living in luxury.
The economic conditions of Iraq’s Sunni Arab population rendered them at prime risk of uprising.
Even the Iraqi Shia authorities implicitly acknowledge it. Earlier this week, officials were briefing the US press that Isis was successfully recruiting "mostly young men between the ages of 16 and 25 who are primarily poor, unemployed and lack an education".
What they meant were poor, young, underprivileged Sunnis – of whom there is an abundance in Iraq.
The economic deprivation suffered by many Sunni Iraqis is connected to, but distinct from, their marginalisation on the political stage.
Sunnis were already beginning to revolt against their Shia oppressors as far back as 2012. In December that year, tens of thousands of Sunnis took to the streets to protest their disenfranchisement.
Iraq has been riven by political and sectarian conflict for decades, but these considerations are liable to obscure related, but distinct, social and economic factors that are crucial in explaining why Isis has been able to overrun the Sunni-dominated parts of the country unresisted.