These members spent quite a bit of time getting to know one another during the campaign, largely through the Serve America PAC started by Representative Seth Moulton, Democrat of Massachusetts, who was among the first troops in Baghdad in 2003.

“When I ran in 2014 against a nine-term incumbent, there was no member of Congress who would even speak with me,” Mr. Moulton said. “So I wanted to create that team for the amazing candidates who were running this time. What was important was building these relationships. They could call or text me at all hours of the night if they needed advice or something. We set up a Slack channel so that we could communicate more as a group.”

Once in Washington, the group immediately gravitated toward one another on bills and other legislative matters. “It’s the trust factor,” said Elissa Slotkin, Democrat of Michigan and a former C.I.A. analyst who served three tours in Iraq. “If Max Rose or Elaine Luria comes to me and says, ‘I’m doing this bill. Do you want to do it?’ they aren’t going to twist the issue and play it for their own advantages,” she said, referring to freshman veterans. “We made the choice to focus on Congress and made Congress like a mission.”

During the government shutdown, Ms. Slotkin and Ms. Houlahan wrote a measure to protect federal workers in subsequent impasses. Representative Mikie Sherrill, Democrat of New Jersey and a former Navy helicopter pilot, seized on news coverage about problems at the Department of Veterans Affairs serving women and quickly got several veterans to sign on to a letter demanding the department secretary, Robert L. Wilkie, fix the system. The group has helped revive discussions about asserting the role of Congress in war authorization.

Veterans are also prone to seeking one another out across the aisle. Mr. Moulton, who served in the Marines, and Representative Brian Mast, a veteran and Republican from Florida, worked to bring together both parties on a conservation bill that pleased environmentalists and commercial fishermen alike.

They can often be seen sliding across the aisle to sit with Republican veterans on the House floor, like Representatives Jim Baird of Indiana and Will Hurd of Texas. “We have a bias toward action because we all served in the trenches in an organization that is apolitical,” Mr. Hurd said. “We knew each other’s ethos.”