More than 11,000 Iraqi troops have been registered as missing since June 10, according to the spokesperson of the General Command of the Armed Forces, Gen. Qassim Atta. Several thousand were either killed or kidnapped, but the majority have deserted their posts, security officials told Al Jazeera.
"We had three divisions in Salahadin, including the troops who abandoned their positions in Mosul. Most soldiers of these troops were either Kurds or Sunnis from the nearby areas and they went back to their homes without being registered as deserters," said a senior Iraqi security official who declined to be named.
On September 2, more than 1,000 family members of missing soldiers believed to be abducted by IS fighters broke into the Iraqi parliament after protesting outside the building. They were demanding answers from the government as to the whereabouts of their loved ones.
The United Nations also called on Iraq to investigate the killings at the Speicher military base. The Iraqi authorities must endeavour "to locate and identify the remains of any who may have been killed, and to undertake all efforts to secure the release of any who may remain in captivity", the UN representative in Iraq, Nikolai Mladenov, said in a statement.
Iraq's Ministry of Defense, the Office of the General Command of the Armed Forces, the Iraqi National Intelligence Service and the Iraqi parliament have formed several investigation committees, including some joint probes, to investigate what happened at the Speicher base.
Four senior military officers who spoke to Al Jazeera blamed corruption, chaos and poor choices in the security commands for the deaths of Iraqi soldiers across the country.
"There was no complicity or betrayal, but the interruption of communications and the lack of experience, professionalism and coordination between thecommands resulted in what happened to the soldiers at Speicher," said a senior Iraqi security official who is linked to the armed forces and is involved in the investigations.
"The most frustrating thing that all the investigation committees have faced is the lack of the accurate numbers of the real missing people from Speicher base over three days, starting from June 11," the official, who spoke on condition of anonymity, said.
Ahmed Ghareeb, an independent Iraqi political analyst, told Al Jazeera that while the killing of the Iraqi soldiers would not lead to further sectarian violence or retribution, the Speicher base incident may "be a [political] card in the hands of Shia parties" that may use the episode "as a pretext to mobilise Sunnis against their politicians".
Meanwhile, he said, "[the] Iraqi parliament's intervention in this case has absorbed the anger of the victims' families, and redirects it to the security institutions which... have failed to provide convincing answers for Iraqis on why this happened".