It has come to be known simply as the "Speicher Massacre." But three years on, families whose loved ones were mercilessly murdered in the Iraq attack are calling on the U.S. to help them find some closure.

"ISIS called me from my son's phone and humiliated me. They said: 'Your son is killed and we threw his body in the river so come and get him,' then they hurled abuses at me," Um Hussein, the mother of a victim identified only as Hussein, recalled to Fox News from her home in a poor part of the southern Iraq city of Nasiriyah. "I didn't hang up. I held on. I held on with the small hope that they might tell me where to find my son's body."

While dozens have been held responsible for the attack, the families say that's not good enough. They want high-ranking government officials -- including the former prime minister -- to also be held responsible because, they claim, the officials abandoned and betrayed the mostly low-ranking military recruits killed in the attack.

On June 12, 2014, right after ISIS seized the country's second-largest city, Mosul, the Sunni Muslim group claimed responsibility for what would become one of the country's bloodiest single attacks on military members. As many as 1,600 unarmed Iraqi Air Force cadets outside Camp Speicher near Tikrit, the hometown of Sunni dictator Saddam Hussein, were massacred.

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"These soldiers went to Tikrit to protect the people and were instead betrayed by the people there. They were sold out to ISIS by local tribes. They were told that they would be helped to get back to their families but instead were handed straight to ISIS," Mohammed, who hails from the south-eastern Iraqi town of Amarah and lost his brother in the Speicher massacre, lamented. "Every commander all the way up the chain to the prime minister's office bears some responsibility for this. We want legal charges against every party responsible."

He, too, is calling on the U.S. and international community to help them re-open the case.

"It has been three years and the majority of families don't know what happened. We don't know who was working and coordinating this attack with the new (post-Saddam) Iraq government," Mohammad added. "This massacre has become a wound that won't close. We feel like our brothers and sons were sold out in a political bargain between corrupt officials and that is why they are trying to hide and close it forever."

Last week a spokesman for Inherent Resolve said in an email to Fox News that the Speicher massacre was "an internal matter for the government of Iraq."

Joint Chiefs Chairman Gen. Joseph Dunford arrived in Afghanistan on Monday for a final assessment on whether to boost U.S. troop levels to counter a nationwide Taliban offensive and increasing terror attacks by the ISIS offshoot called Islamic State-Khorasan Province, or IS-K.

Dunford's report on the deteriorating security situation will weigh heavily in Defense Secretary Jim Mattis' decision, expected next month, on the long-standing request of Army Gen. John Nicholson, commander of U.S. Forces-Afghanistan and NATO and coalition troops, for an increase of 3,000 to 5,000 troops in the Force Management Level.

In House and Senate hearings last week, Mattis said President Donald Trump had given him authority to set the force level in Afghanistan, which now stands at about 8,400 troops. However, the SecDef said a "little under 10,000" are now in Afghanistan, possibly because of overlaps in regular troop rotations. Trump had already granted Mattis similar authority to set troop levels in Iraq and Syria.

NATO and coalition troops have about 5,000 troops in Afghanistan, and Mattis has signaled that he expects more commitment from allies, either with troops or funding.

Mattis also told Congress that he will present a revised regional strategy, in coordination with Secretary of State Rex Tillerson, to Trump in mid-July. In doing so, he disputed published reports that he had already signed off on sending 4,000 more U.S. troops into the nearly 16-year-old conflict in Afghanistan.