SAN ANTONIO — The women assaulted by their Air Force training instructor don't sleep much these days and when they do, he sometimes haunts their dreams.

They testified Saturday about being suddenly unable to relate to husbands, boyfriends and even fathers and brothers after they were sexually assaulted. One said her fear during a tour of duty in Afghanistan was heightened by soldiers who reminded her of her instructor, and she warned her younger sister not to enlist in the Air Force. Another said she's now afraid to be behind closed doors with any man.

Staff Sgt. Luis Walker was sentenced to 20 years in prison Saturday for crimes that included rape and sexual assault. He is among 12 instructors investigated for sexual misconduct toward at least 31 female trainees at one of the nation's busiest military training centers. Six have been charged with crimes, and the counts against Walker were the most severe. He could have faced life in prison.

Prosecutors say he used his position as a military trainer at Lackland Air Force base in San Antonio to gain female recruits' trust, and then he made illicit sexual advances. Walker's court-martial included testimony from 10 women, one of whom wept as she described him luring her into his base office and sexually assaulting her on a bed, ignoring her pleas to stop.

Walker showed little emotion as the sentence was read, but he appeared to have tears on his face later as he gazed at his wife, Yeimi. Both had cried earlier, while asking the military jury for leniency and a shorter sentence so that he would be able to spend time with his two sons, ages 7 and 4.

"I ask for my family's sake, for my two boys right there," Walker said, wheeling around to look at the youngsters, who sat squirming and chattering back and forth with no understanding of the proceedings. "I ask that I am allowed to have a future with them."

Walker's stepfather, sister and wife all testified on his behalf, describing an earnest teen who grew up in a tough corner of Brooklyn, dreamed of joining the Air Force from the age of 14 and arranged to graduate from high school early so he could enlist.

"All of his dreams are shattered and our dreams because I was so proud of him," said Herbert O'Connor, Walker's stepfather.

Walker was taken after the hearing to a temporary lockup at Lackland to await transfer to a permanent prison.

The six men and woman who served on the military jury are barred from discussing their deliberations so it's impossible to know if the testimony swayed. But the victims' testimony was equally as emotional. Five spoke during sentencing, including four who are still in the service.

"In Afghanistan, I was a little bit more scared of everything," said one, who said Walker sexually assaulted her last year, while she was a trainee at Lackland.

"I couldn't work with certain individuals," she added, "just since they remind me of Staff Sgt. Walker."

Prosecutors say Walker sexually assaulted or had improper sexual or personal contact with at least 10 female recruits from October 2010 through January 2011. The Associated Press does not usually identify victims of sexually assault.

The same victim said her 15-year-old sister talked about joining the Air Force, and "I've absolutely told her she's not allowed anywhere near" it. Other victims said they had the same advice for female relatives and friends.

"I don't enjoy the military anymore," one said. "I don't want to be in it."

Another victim spoke of being unable to sleep at night "because I somehow feel he terrifies me." That victim also said the trauma she felt from the assault continued to plague her after she left the military.

It's gotten to where I had anger issues even at work," she said. "If anyone makes even the slightest sexual reference, I go off. I have zero self-control."

Lackland is where all Air Force recruits go through basic training. It has about 475 instructors for about 35,000 airmen who graduate every year. While one in five recruits are female, most instructors are male.

While the alleged sexual misconduct among instructors at the base apparently began in 2009, the first woman didn't come forward until last year. The women who testified against Walker said they didn't tell anybody at first because they feared being booted from the Air Force.

But even those who remained in the service said their careers had been ruined by fear, along with every other part of their lives.

"Every time I'm smiling or I'm laughing, I feel like its fake because I'm empty," one said. "I'm not happy on the inside anymore. I'm not myself."

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  • Start of War: Oct. 7, 2001

    <em>American soldiers hide behind a barricade during an explosion, prior to fighting with Taliban forces November 26, 2001 at the fortress near Mazar-e-Sharif, northern Afghanistan. (Photo by Oleg Nikishin/Getty Images)</em>

  • Number of U.S. Troops in Afghanistan: 88,000

    <em>US Marines with the 26th Marine Expeditionary Unit deployed from the USS Bataan's Amphibious Ready Group arrive December 14, 2001 at an undisclosed location with field gear and weapons. (Photo by Johnny Bivera/Getty Images)</em>

  • Number of Troops at War's Peak

    <em>U.S. Marines begin to form up their convoy at a staging area near Kandahar, Afghanistan, as they await orders to begin their trek to Kandahar to take control of the airfield 13 December, 2001. (DAVE MARTIN/AFP/Getty Images)</em><br><br> Number of U.S. troops in Afghanistan at the war's peak: About 101,000 in 2010. Allies provided about 40,000.

  • Withdrawal Plans

    <em>U.S. President Barack Obama delivers a televised address from the East Room of the White House on June 22, 2011 in Washington, D.C. (Pablo Martinez Monsivais-Pool/Getty Images)</em><br><br> Withdrawal plans: 23,000 U.S. troops expected to come home by the end of the summer, leaving about 68,000 in Afghanistan. Most U.S. troops expected to be out of Afghanistan by the end of 2014, though the U.S. is expected to maintain a sizeable force of military trainers and a civilian diplomatic corps.

  • Number of U.S. Casualties

    <em>American flags, each one representing the 4,454 American soldiers killed in the Iraq and Afghanistan wars, move in the breeze at The Christ Congregational United Church March 17, 2008 in Miami, Florida. (Photo by Joe Raedle/Getty Images)</em><br><br> Number of U.S. casualties: At least 1,828 members of the U.S. military killed as of Tuesday, according to an Associated Press count. According to the Defense Department, 15,786 U.S. service members have been wounded in hostile action.

  • Afghan Civilian Casualties

    <em>Asan Bibi, 9, sits on a bench as burn cream is applied to her at Mirwais hospital October 13, 2009 Kandahar, Afghanistan. She, her sister and mother were badly burned when a helicopter fired into their tent in the middle of the night on October 3rd, according to their father. (Photo by Paula Bronstein/Getty Images)</em><br><br> Afghan civilian casualties: According to the United Nations, 11,864 civilians were killed in the conflict between 2007, when the U.N. began reporting statistics, and the end of 2011.

  • Cost of the War

    <em>An Iraqi man counts money behind a pile of American dollars in his currency exchange bureau in Baghdad on April 11, 2012. (ALI AL-SAADI/AFP/Getty Images)</em><br><br> Cost of the war: $443 billion from fiscal year 2001 through fiscal year 2011, according to the Congressional Research Service.

  • Number of Times Obama Has Visited Afghanistan

    <em>US President Barack Obama speaks to troops during a visit to Bagram Air Field on May 1, 2012 in Afghanistan. (MANDEL NGAN/AFP/Getty Images) </em><br><br> Number of times Obama has visited Afghanistan: 3 as president, including Tuesday, and 1 as a presidential candidate.