A retired Army Special Forces sergeant major and combat veteran of Iraq and Afghanistan endorsed Paul Nehlen for Congress Monday in an exclusive interview with Breitbart News.

Andrew Wilson told Breitbart News he decided to support Nehlen after the two men had frank conversations about problems facing the country. Nehlen is a Wisconsin businessman challenging Speaker Paul D. Ryan in Tuesday’s Republican primary.

“It was his attitude and his genuine concern for military veterans and their families, the security of the U.S.–and jobs,” said the president and CEO of Quiet Professionals, a Tampa, Florida-based consultancy.

“There was quite a bit of back and forth there,” he said. “I wanted to find out about his principles and values and it sounded like we were on the same track.”

The retired sergeant major, who was a 14-year veteran of a special operations mission unit, said another factor in his decision was the example of retired Army Maj. Gen. Paul Vallely to endorse Nehlen.

Writing in a special op-ed for Breitbart News, Vallely said Ryan failed to live up to his committments to the people of Wisconsin’s First Congressional District and the American people,by his failure to fight to secure the borders and maintain a strong national defense.

Because I love this nation, and as a matter of conscience, I unequivocally oppose the re-election of United States House of Representatives Speaker and representative of the First Congressional District of Wisconsin, Paul Ryan, and place all my support behind his opponent, Paul Nehlen.

Wilson said his own concerns for Ryan’s support of open immigration and trade deals, such as the Trans-Pacific Partnership, are not just theoretical.

“My concern about all that is that as I work overseas–and it is completely different for somebody who served in the military, especially for someone who has served in some of the units that I have served in–I have seen how things really work,” he said.

“I think most Americans have an unrealistic view of the rest of the world, simply because they have not been immersed in those types of environments before,” he said.

“It is incumbent upon us, especially members of the special operations, to be able to serve and protect the United States and certainly our homeland,” he said.

“I think there is a lot of misunderstanding about people who can come in and out the country illegally and what that means,” he said.

Wilson said when illegal aliens pass in and out of the country without proper screening and without the government being able to track and monitor then, it creates opportunities for terrorists and other agents hostile to the United States to plan and execute attacks upon the American people in the shadows.

“They can quickly form cells,” he said. “They can mobilize when the time comes or they can execute subversive acts–and I think those things are starting to happen on a small scale now.”

The retired sergeant major said if the policies supported by Speaker Paul D. Ryan continue those cells and their activities will grow and mature and become an even greater danger.

“I see those things growing on a larger scale down the road if we continue with the same polices and procedures that we have had–certainly when it comes to immigration.”