Rep. Mac Thornberry announced his retirement Monday, becoming the sixth Texas Republican planning to not run for re-election in 2020.

“I believe that the time has come for a change. Therefore, this is my last term in the U.S. House of Representatives,” he wrote in a statement.

Mr. Thornberry, the top Republican on the House Armed Services Committee, has served in Congress for more than two decades.

More than a dozen of House GOP lawmakers have announced their plans to retirement, with the party losing prominent members like Reps. Susan Brooks of Indiana, the NRCC’s recruitment chair, and Will Hurd, the House GOP’s only African-American member who represents a competitive swing district in Texas.