Dozens of the fighters, who helped avert a civil war and were crucial to curbing Iraq's sectarian violence when it peaked in 2006 and 2007, have been killed in recent months in acts of retaliation.
The latest reprisals saw six of the former Sunni rebels killed in a village north of Baghdad on Thursday, in what police said was an Al-Qaeda attack.
As US forces steadily leave the country the Sons of Iraq, also known as the Sahwa (Awakening) force, feel abandoned and its men complain of being betrayed by the nation they fought to defend.
"If our houses are being attacked and destroyed by the terrorists even before the withdrawal, what will happen to us when the US forces leave?" asked Majid Hassan, a Sahwa commander in Samarra, a Sunni-stronghold in Salaheddin province north of Baghdad.
Hassan's own home was struck by a bomb on August 13, injuring his leg and wounding three members of his family. Parents, wives, sons and daughters of Sahwa members have also been viewed as traitors and killed in revenge.
"The terrorists say, 'You are the Sons of America' and we will not keep any one of you alive after the withdrawal," the 52-year-old, from the Bubaz tribe and a farmer before taking up arms in 2006, told AFP.
"We will not be able to destroy Al-Qaeda if the Americans are leaving."
The tribe formed a militia against Al-Qaeda and sided with the US military when its chief was executed.
The United States has pulled tens of thousands of soldiers out of Iraq in recent months, with numbers now below 50,000, less than a third of the peak level in 2007, ahead of a complete pullout in December 2011.
The Sons of Iraq moved under the control of the Shiite-led Iraqi government in early 2009 in a tense handover -- ministers have always viewed the force with suspicion -- and they have since complained of shoddy treatment.
The militia has recorded hundreds of fatalities since its formation, suffering almost daily bombings and shootings at checkpoints and a rise in attacks this year, its members say.
"The government has not shown any cooperation with the Sahwa, to help us get on with our duties," said Mohammed al-Naqeeb, head of the Sons of Iraq at Al-Tharthar lake on the border of Salaheddin and western Anbar provinces.
"As the full withdrawal of American troops approaches, the situation for the Sahwa becomes more dangerous," he said.
In Samarra in February 2006, alleged Al-Qaeda fighters destroyed the golden dome of the al-Askari shrine, which houses the remains of two imams venerated in Shiite Islam, triggering nationwide sectarian violence that blighted the country in 2006 and 2007.
It was later that same year that the Sahwa began to emerge across the west and north of Iraq, and in Baghdad, paid a monthly salary by the US.
The force numbered 118,000 at its peak. When control over the militia passed to the Iraqi government in April 2009 Baghdad promised to integrate 20 percent of the men into the police or army and find civil service jobs for many of the rest.
However, 52,000 of the fighters are still waiting for new employment.
The fighters earn between 300,000 and 600,000 Iraqi dinars (255 and 510 dollars) per month, according to Khalid al-Nuaimi, the militia leader in Diyala province.
But since the transfer of responsibility their wages have often been paid late, and the US withdrawal has sparked disquiet among the Sons of Iraq that their security is being compromised.
The defence ministry, however, insists that the former rebels will not be forgotten, and the government has pledged they will be used to gather intelligence against insurgents.
"The war against Al-Qaeda is a war of intelligence and lots of leaders from Al-Qaeda have been arrested after tip-offs given by the Sahwa," said Zuhair al-Chalabi, the top Iraqi government official dealing with the Sahwa.
For now, those who remain at their posts remain the targets of insurgents who regard them as traitors.
Just last month, a suicide bomber blew himself up among a crowd of militiamen waiting to receive their wages outside Baghdad, killing 45 and wounding 46.
"Attacks have increased with the approach of the US withdrawal from Iraq," said Majeed Abbas, the militia's leader in Samarra, commanding 2,300 fighters across the city.
"Since responsibility fell on the Iraqi government, we have suffered from a lack of support and salaries."
The 46-year-old added: "This negligence has given the terrorists motivation to target Sahwa forces and their leaders.
"Each passing day, we record another attack against us."
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