(CNN) Sgt. La David Johnson married his childhood sweetheart and was expecting his third child.
Staff Sgt. Bryan Black learned Hausa because he wanted to communicate directly with Nigeriens.
Staff Sgt. Jeremiah Johnson earned more than a dozen military commendations.
And Staff Sgt. Dustin Wright came from a family deeply rooted in military service, dating back to 1812.
All four died in an ambush on October 4, after helping local forces in Niger combat terrorists.
They came from across the country, each leaving a profound legacy on their communities. Here's what we know about their lives and service of the four soldiers killed:
Even as an adult, Johnson had a playful spirit, once demonstrated by his unusual method of commuting when he worked in the produce section at Wal-Mart.
"He would remove the front wheel of his bike and ride to and from work, earning him the title of 'Wheelie King,' " his obituary said.
Johnson lost his mother as a young boy and was raised by relatives. Growing up in South Florida, he loved playing football. And during his early school years, he met Myeshia Manual, who later became his wife.
Johnson studied mechanical engineering and enlisted in the Army in 2014.
He is survived by his wife and children, Ah'leeysa Jones and Ladavid Johnson Jr. Before he died, Johnson was expecting his third child, La'Shee.
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Ever since he was a child, the Green Beret medic was incredibly strong-willed and competitive.
"He became irritated in the 4th grade when his brother won a trophy at a chess tournament and he didn't," his obituary said. "He turned his frustration into action, spending an entire summer studying and learning chess. Bryan then dominated scholastic chess in Washington state, tied for 2nd in the nation in the 6th grade, and competed well at the adult level."
He later tackled and mastered other fields, including carpentry, stock trading, martial arts, roofing and medicine.
Black enlisted in 2009 and served as a special forces medical sergeant.
"During his previous deployment to Niger he learned the local dialect Hausa because he wanted to be able to communicate directly with the people," Black's obituary said. "He also spoke French and Arabic. Bryan was often in high demand within his team and with locals due to these efforts."
News of Black's death devastated his hometown of Puyallup, Washington.
"It's absolutely heart wrenching," neighbor Whitney Kamel told CNN affiliate KOMO.
Kamel said she is friends with the Black's mother, Karen, and is grateful for the family's sacrifice.
"I want to personally thank Karen and her family and her son for laying down his life for us," she said.
Black is survived by his wife, Michelle Richmond Black, and sons Ezekiel and Isaac.
Johnson was a chemical, biological, radiological and nuclear specialist, the Department of Defense said.
He enlisted in the Army in 2007 and earned more than a dozen awards and decorations, including the Army Commendation Medal, the National Defense Service Medal and the Global War on Terrorism Service Medal.
Johnson is survived by a wife and two daughters, CNN affiliate WLWT said.
Wright's calling was to serve in the military -- and not just because his family has served since 1812, his brother said.
"It didn't matter if he'd known you for a day or whole life -- the man was a servant and he loved people," Will Wright told CNN affiliate WRAL.
"He found a way for him to serve others, to sacrifice and to love people and do it in some of the worst environments in the world. To his final breath, he was doing that."
The last time Will Wright spoke with his younger brother, Dustin, was on September 24 -- the staff sergeant's 29th birthday.
They "talked about how things were going, the ups and downs," Will Wright told WRAL. "Talked about his girlfriend, talked about his plans when he came home, where he was going and some potential moves in his future."
"The last words I said to my brother were 'I love you." Last words he said to me were 'I love you,'" Will Wright said.
Staff Sgt. Wright's death marks a grim first in the family's two centuries of military service.
"To our records, we had not lost a single member until Dustin. That's 205 years. That's a good run," his brother said. "If once every 205 years, this is a price we pay, then that's what it takes."