By Ashley Fantz, CNN

In the United States, servicemen and women learn the Soldier's Creed during basic training. It's simple and direct, and makes clear a warrior's cardinal sin in one line: "I will never quit."

Other modern armies have similar statements of faith. The idea of dropping weapons and running away from an enemy tends to shock.

Defense Secretary Ash Carter told CNN that the Iraqi army showed "no will" to fight. To some, his words suggested weakness and cowardice.

But a number of scholars and military experts say the problem with the Iraqi military is far more complex.

Starting from scratch

Think about what it would be like to fire every senior employee at a company and leave the interns in charge.

In 2003, Lt. Gen. Mark Hertling was in Baghdad. He was meeting with Iraqi counterparts when his assistant passed him a note. It said that then-President Bush's envoy to Iraq Paul Bremer had announced that the Iraqi army would be dissolved.

Those with any experience were out, and so, too, were those in civil service. The idea was to get rid of anyone with a government job who belonged to Saddam Hussein's Baath Party.

That meant thousands of people. Most Iraqis people joined the party just to get on in life -- there was just no other way for many. They pledged their loyalty even if they didn't truly mean it just to have a job, to feed their families. Party affiliation didn't necessarily mean a person was loyal to Saddam or did bad things in his name.

Ultimately, firing all military members meant throwing away what had been a highly capable professional military, one that predated Saddam.

The dominoes began to fall.

"That was at least part of the insurgency we started seeing in 2003 and 2004 -- many of the people we started fighting were disgruntled former fighters who knew how to plant bombs and fire weapons," Hertling said.

Firing all the Baathists made rebuilding Iraq very hard, he said.

"We were trying to build schools and couldn't hire teachers because they were members of the Baathist party," he said.

Electrical workers, water system professionals -- you name it -- they weren't eligible for employment. Day to day life was a chore and distrust of the U.S. and its allies mounted.

Playing Sunnis against Shiites

Military recruitment has been a challenge. U.S. troops had to start with the basics. They were trying to teach young Iraqi men to aim, Hertling recalled, a new concept for many who had traditionally employed the "pray and spray" technique -- sticking a rifle on a berm and firing randomly.

While fresh recruits were learning to be professional soldiers, leadership had to be drawn in also. But Hertling and Mansoor said their effort was undercut beginning in 2006 when Nuri al-Maliki, a Shiite, was sworn in as prime minister. Al-Maliki set about replacing Sunni commanders with Shiites loyal to his government, they said.

"You lose all trust in the leadership," said Hertling. "That is extremely difficult to rebuild."

"I think they (Iraqi soldiers) are confused about what they are fighting for," said Marina Ottaway, a senior scholar with the Woodrow Wilson Center's Middle East Program. "You can be well trained and have the equipment you need and it doesn't matter if you aren't clear what your goal is."

If you're a Sunni and you've seen the kind of favoritism of the al-Maliki government, why would you trust that the new government of Haider al-Abadi, also Shiite, won't fill military posts with political appointees from his own ethnic background?

"A lot of Sunnis aren't convinced that ISIS is worse than the government," Ottaway said. "You shouldn't underestimate the resentment among Sunnis toward Baghdad."

On their own

Shortly before American troops withdrew, top officials praised the Iraqi military's prowess. Then-Defense Secretary Leon Panetta spoke about "sustained progress" in December 2011 in Baghdad.

"The Iraqi army and police have been rebuilt and they are capable of responding to threats; violence levels are down; al Qaeda has been weakened; the rule of law has been strengthened; educational opportunities have been expanded; and economic growth is expanding, as well," he said at the time.

But Col. Peter Mansoor, the founding director of the U.S. Army and Marine Corps Counterinsurgency Center, worried at the time. There was no institutional foundation for creating solid soldiers down the road, no way to foster new generations of troops. Iraq had no West Point, no ROTC program, no Pentagon.

Iraq "really could have used military advisers well past 2011," Mansoor told CNN Tuesday. "They could have kept check."

A battlefield leadership vacuum

As part of his anti-ISIS strategy, President Barack Obama has ordered hundreds of military advisers to the region.

The hope is that will offer some professional direction, but experts believe leadership must come from within the Iraqi community.

"Why do soldiers fight? They join because they believe in a higher cause -- protecting religion, their nation, defending against a foreign nation," Mansoor said. "But why do soldier stay and fight? Soldiers aren't individuals. They are part of a unit. And that unit is led by a commander. If they don't trust their commander ... if there is no leadership, there is nothing."

It's still unknown if and how commanders are being held responsible for troops refusing to fight ISIS in Ramadi.

When no one is looking

By the summer of 2014, Maliki's grip on power was coming loose. There was a new enemy in Iraq and as ruthless as al Qaeda -- the Islamic State seemed to have developed its strategy from a slasher flick.

When Mosul fell to ISIS in 2014, it was not because ISIS outnumbered Iraqi troops. The troops just dropped their guns and split -- a move that seemed to initially puzzle just about everyone.

It became clear by the end of last year, however, that the troops the U.S. trained had more severe problems than imagined.

Al-Abadi announced that he had discovered at least 50,000 "ghost soldiers" -- members of the armed forces who pay off their commanders with a portion of their salaries so they don't have to man their posts. Fake names turned up on military rolls, he told Parliament.

The prime minister promised a deeper investigation, and said he expects more bogus names will be found.