Just five days before Ekaterine Bautista planned to become an American citizen, she got a call from the federal government: Her swearing-in ceremony had been canceled pending further investigation.

Bautista was devastated. An illegal immigrant from Mexico, she had served six years in the U.S. military — including a 13-month tour of duty in Iraq — and was eligible to apply for naturalization under a decades-old law.

But approval of her case depended on the discretion of citizenship officials. Bautista had served in the military under a false identity, that of her U.S. citizen aunt, Rosalia Guerra Morelos.

She passed the civics exam, completed all the paperwork and received a letter telling her to show up at the Los Angeles Convention Center on March 31. Then the call came.

“Yeah, I made a mistake,” Bautista, 35, said. “But if you look back at my records, I never did anything wrong in the military. On the contrary.”

Sitting in her father’s home in East Los Angeles, Bautista proudly looks through a thick binder of commendations and certificates, including the Combat Action Badge. She says she was promoted to sergeant within three years. She pulls out photos: one showing her hugging her friends in her unit in Germany, another showing her in uniform at the base she guarded in Iraq. The name on her uniform reads Guerra.

Like many other soldiers, Bautista decided to enlist just days after Sept. 11.

“It was a calling,” said Bautista, who was a teenager when her mother brought her to the U.S. “I felt the need to join because it was the right thing to do, and also because of my daughter. I had to protect my daughter.”

She called an Army recruiting office, but they told her that a Mexican passport wasn’t enough and that she had to be a U.S. citizen or a green-card holder to enlist. So she asked her family for permission to use the identity of her aunt, a U.S. citizen who lived in Mexico. With their blessing, Bautista walked into a Montebello recruiting office and introduced herself as Rosalia Guerra Morelos. She presented a driver’s license, birth certificate and Social Security number.

As part of the 1952 Immigration and Nationality Act, noncitizens who serve in the military one year during peace time or one day during wartime are eligible to apply for fast-tracked citizenship. In 2002, President George W. Bush issued an executive order and invoked the wartime law as of Sept. 11, 2001.

Between September 2001 and March 2010, more than 58,000 men and women in the armed forces were naturalized, according to U.S. Citizenship and Immigration Services. The agency doesn’t track how many were undocumented.

There have been similar cases to Bautista’s, including that of Mexican illegal immigrant Liliana Plata, who bought a stolen Social Security card in Los Angeles so she could join the military and later became a decorated airman serving in Iraq as Cristina Alaniz. She was honorably discharged from the Air Force in 2003 after the real Alaniz discovered her identity had been stolen.

Many immigrants have been raised in the U.S. and are drawn to the armed forces for the same reasons as native-born Americans: a steady job, the military lifestyle and patriotism, said Margaret Stock, an Alaska-based immigration attorney who specializes in military cases and is an officer in the Army Reserve.

“Many are very patriotic, even though it’s not officially their country,” she said, speaking as a private citizen.

Unfortunately, Stock said, cases like Bautista’s are difficult to detect because there is no biometric registry of U.S. citizens. They are also potentially dangerous, as American citizens have access to different jobs and security clearance in the military, she said.

Eugene Fidell, who teaches military justice at Yale Law School, said that enlisting under a false identity is a crime and is taken very seriously by the government. “It’s deeply frowned upon,” he said. “It really is fraud.”

But in some cases, he said, if the person served honorably, the government should exercise discretion and grant citizenship.

When she enlisted, Bautista said, she didn’t know that immigrants who served in the military could become citizens.

After basic training, Bautista was stationed in Germany and assigned as a food service specialist. In 2004, she deployed to Iraq and guarded the base in Baqubah.

On June 8, 2004, a car driven by a suicide bomber approached the gate and immediately exploded. “It was like in the cartoons — people flying everywhere,” she said.

Bautista was knocked off her feet. Three people landed on top of her. “They were my shield,” she said. “They saved me.”

After a few seconds, Bautista said, she stood up and saw blood and body pieces everywhere. She ran to get medical supplies and helped bandage fellow soldiers and Iraqi citizens who worked on the base. Bautista’s commanding officer and two Iraqi civilians were killed. More than a dozen soldiers and Iraqi citizens were wounded. “It was chaos,” she said, tears falling down her face.

Back in Germany, she settled into the routine of military life. She fell in love, but even he didn’t know her true identity. She didn’t tell fellow soldiers that she had a daughter.

But in 2008, Bautista was called into an office by her superiors. They told her they knew who she really was. She asked to talk to an attorney.

“I tried to retain my military bearing at all times,” she said. “I tried not to show any emotion.”

But inside, she was scared. Would she be arrested? Kicked out of the Army? Deported? The military launched an investigation and confiscated the documents bearing her aunt’s name.

Several of her fellow soldiers and superiors wrote letters on her behalf. In one, a superior described how Bautista helped the wounded before tending to herself after the explosion and wrote that she was “an exceptional role model.” “It will be a shame for the Army to get rid of an outstanding soldier like this,” the letter read.

In the end, Bautista was honorably discharged and arrived in Los Angeles in July 2009. Having to leave the military, she said, still hurts. Even now, she wishes she could return to Iraq.

“When you are in a war zone, you create like a family,” she said, her voice cracking. “It’s hard to leave your brothers and sisters behind.”

Her daughter, Mizhrua Bautista, 15, who was born in the U.S., said she understands why her mother wanted to join the military so badly that she used a different name. “Not a lot of people are willing to do that and put their life in danger to help out her country,” she said. “I want to see her get her citizenship.”

After the call canceling the ceremony, a follow-up letter said citizenship officials wanted a passport she had obtained fraudulently. Bautista’s attorney, Noemi Ramirez, said she had already given citizenship officials a receipt showing that the military had confiscated the passport.

Ramirez said she admires her client’s dedication to America and said she deserves citizenship. “The fact that she served in the military, went to Iraq and was in the line of fire outweighs the immigration violation she committed,” she said, adding that Bautista was not high-ranking and did not have security clearance.

U.S. Citizenship and Immigration Services spokeswoman Mariana Gitomer said she couldn’t comment on the case but said it’s not unusual for the agency to need further clarification.

“It doesn’t mean that they are not going to be naturalized,” she said. “It just means we have to look into the case a bit more.”

Until her case is resolved, Bautista can’t drive, work or receive veteran’s benefits. Even though she wishes she could have done so with her own name, Bautista said she doesn’t regret joining the military.

“Now that I look at my daughter,” she said, “it was worth it.”

anna.gorman@latimes.com