(CNN) -- Ike Skelton, who served Missouri for 34 years in the House until 2011, died Monday at 81, Democratic leaders said.
President Barack Obama said Skelton "was beloved and respected by colleagues on both sides of the aisle."
House Minority Leader Nancy Pelosi called Skelton a "selfless patriot."
"He fought to bridge what he called 'a chasm between those who protect our freedoms and those who are being protected,' " she said in a written statement. "From their quality of life to their readiness for war, he made sure that every man and woman in uniform who put their lives on the line would receive the support they had earned and the deepest respect they deserved.
She didn't mention where Skelton died or a cause of death.
"Ike Skelton was a dedicated public servant committed to ensuring our national security and providing for the greater good. He was also a friend, a mentor and a truly unique individual," said Rep. Adam Smith of Washington state.
Skelton, a champion of the military, served as the chairman of the House Armed Services committee during his last two terms.
"As chairman of the Armed Services Committee, he was a fierce and relentless advocate for the men and women in uniform. As a friend and mentor, he was a compassionate individual who truly cared about the well-being of others," Smith said.
Skelton was defeated in November 2010 by Republican Vicky Hartzler for his seat in Missouri's 4th District, which includes Columbia.
After he lost his seat in Congress, Skelton joined the law firm of Husch Blackwell, which is based in Kansas City and also has an office in Washington. He worked on the firm's technology, manufacturing and transportation team, according to Husch Blackwell's website.
"Saddened at passing of my friend & role model Congressman Ike Skelton. A great leader & true public servant," Missouri Gov. Jay Nixon said on Twitter.
Skelton, whose full name was Isaac Newton Skelton IV, had three sons with his first wife, Susan, who died in 2005. He married Patty Martin in 2009.