The divisions within Iraq, never healed since the 2003 invasion, are being newly inflamed by the increasingly sectarian nature of the conflict in Syria. Once the fighting in Syria ends - and no matter how it ends - the tensions produced in its neighbours can be expected to become more pronounced, and more dangerous.
The New York Times reported this week that Iraqi Shiites in growing numbers are filtering into Syria to fight in defence of the Assad regime. These militants may well find themselves in firefights against their countrymen, Iraqi Sunnis who are fighting with the opposition.
The outline of overtly sectarian conflict looms clearly through the fog of battle in Syria. Iran, certainly, is to blame for part of this, and it operates largely through Iraq.
This week, in a fine theatrical performance, Iraq forced down an Iranian cargo plane en route to Damascus, to search it for weapons. The Iraqis found none - and fooled no one.
Without support from Tehran's allies in Iraq, Prime Minister Nouri Al Maliki might not be in office today, and he knows it. To be sure, many in Iraq's Shia majority are wary of Iranian influence, with the Iran-Iraq War remaining a vivid memory. But Iran has close ties, overt and covert, with powerful Shia groups in Iraq, as proxies or partners. So Mr Al Maliki must listen to Tehran more than a sovereign premier should.
If only he would cooperate so well with his fellow Iraqis. By concentrating evermore power into his own hands, and reserving positions of responsibility in Baghdad exclusively for his loyalists, the prime minister is building up fierce resentments, and the results cannot be good.
The bitter truth is that such policies fail to even benefit Mr Al Maliki's own constituencies. The rash of shootings and bombings over the Eid weekend predominantly targeted Shia communities. Al Qaeda in Iraq, and other radical Sunni groups, appear to be resurgent. But the security forces that are now dominated by Shia loyalists cannot take the fight to the militants without turning it into a sectarian war - "justice" in such a struggle is a subjective value.
The more starkly sectarian the Syrian struggle becomes, the more it will pull at its neighbour's ill-healed wounds. Mr Al Maliki has managed to cling to power, despite technically losing the 2010 elections. But a wily politician is not the same as a statesman, which is what Iraq desperately needs now.