Maj. Lisa Jaster, facing camera, helps another soldier at Ranger School on April 21 in Fort Benning, Ga. (Spec. Dacotah Lane/U.S. Army)

Over six months of training at the Army’s famously difficult Ranger School, Maj. Lisa Jaster grew to realize something, she said: She was “the unicorn.”

The engineer officer graduated in October, becoming one of just three women in that inaugural class to complete training and earn the right to wear the coveted Ranger tab on her uniform. Tuesday night, she will be one of 23 Americans joining the first lady at President Obama’s last State of the Union address — a group the White House has selected to tell the story of his presidency.

The decision to invite Jaster — as well as others, including a Syrian refugee, a plaintiff in the lawsuit that legalized same-sex marriage nationwide and two early supporters of Obama’s first White House bid — reflects the president’s determination to adopt a defiant pose during his speech to the nation. While the first lady’s box provides a visual representation of what he has done in office, it also shows where lawmakers have blocked his agenda: One seat will be left vacant to symbolize the Americans killed and injured by guns each year.

White House senior adviser Valerie Jarrett said in an interview that the first lady’s guests represent both the trajectory of Obama’s presidency and the role everyday citizens have had in shaping it. “They embody what’s great about America, when ordinary people who are willing to make their voices heard, come together and are able to move our country forward in a positive direction,” she said.

Obama and his aides have been eager to highlight the success of the Army Ranger School’s first three female graduates, as well as the military’s decision to open all combat roles to women. Although these moves have come under fire in some quarters, administration officials have pointed to them as areas where the president has expanded opportunities for women in U.S. society.

“She and others represent all the infinite possibilities, that people who are prepared to work hard can break all kinds of barriers and achieve their dreams,” Jarrett said of Jaster. “Every young girl can have the opportunity to do what she did, if that’s their dream.”

Jaster was one of 19 women who attempted the Army Ranger course in April, when it was opened to female service members for the first time. In some ways, she was the most unusual of them: While most troops who attend are on active duty, male and in their 20s, she was a 37-year-old officer who was activated from the Army Reserve to go, temporarily leaving behind a successful career as an engineer with Shell Oil in Houston and her husband and two young children for a shot at making history.

Jaster said in a phone interview Friday that she wants to show that there are men and women capable of succeeding in almost any role.

“I want my presence to symbolize the fact that there are competent people out there, and as long as the standards don’t change, the best person for each job needs to be placed in that job,” she said.

Jaster said that she and the other women had to earn respect from their male peers, some of whom considered it bizarre that women were at the school. She was held back, or “recycled,” in each of the three phases, meaning she had to establish and reestablish relations with male students numerous times.

When Earl Smith first met then-Sen. Obama in an elevator in February 2008 at the Hyatt Regency in Austin, he gave Obama something that he would carry with him for the rest of the campaign. Smith will be sitting in the first lady’s box for the president’s last State of the Union address Jan. 12. (Jayne Orenstein/The Washington Post)

“I was the unicorn,” she said. “When they saw me, it was like spotting a unicorn. It was odd, funny, they didn’t know how to act. That was the feedback I got. But, each group, there was a single moment where they transitioned to I was just Ranger Jaster. I stopped being the girl, I stopped being the female, I stopped being the unicorn and I became their battle buddy, their Ranger buddy, their peer. Each of those little spikes reminded me why I went, which was just to prove that you should expect higher. Expect more.”

When the Army opened the Ranger School to women last year, it was on a temporary basis, as the military performed research required in 2013 by former defense secretary Leon Panetta on how it could more fully integrate women in the future. The school is considered the Army’s premier leadership school, and historically, about half of all students pass.

Three women — Jaster, Capt. Kristen Griest and 1st Lt. Shaye Haver — would make it through the first phase of training and head to the mountains, and that was after multiple recycle attempts. Haver and Griest would go on to complete the mountain phase and swamp phase on the first try and become the first two female graduates in August, but it took Jaster two tries on each. That left her as the only remaining woman in Ranger School from August through her graduation in October.

“When I recycled swamps, I was surprised. I was extremely disappointed in myself and I could barely figure out how to call my husband and tell him that I had to stay for another four weeks, because there was a one-week break before the next class started up. That was definitely the lowest point,” Jaster said.

Still, opening up all U.S. combat roles to women is a less controversial issue than how to handle the applications of those seeking asylum from Syria and Iraq. The move to invite Refaai Hamo, 55, who fled Syria in 2013 and was cleared by U.S. authorities to arrive in Detroit last month, comes as Obama has sought to counter Republican calls to bar Muslim refugees in the wake of terrorist attacks in Paris and San Bernardino, Calif. Hamo’s wife and daughter were killed when a bomb struck their home, prompting him to flee to Turkey in 2013 before attempting to enter the United States. He and his four surviving children live in Detroit, and his ordeal was featured in a popular blog, Humans of New York.

First lady Michelle Obama’s other guests include Connecticut Gov. Dan Malloy (D), whose state raised the minimum wage to $10.10 an hour; Microsoft chief executive Satya Nadella, who immigrated to the United States from India; and Spencer Stone, an Air Force staff sergeant who helped two other Americans foil a terrorist attack on a French train.

David Nakamura contributed to this report.