"When you get somebody who is the president of the United States who understands precisely what you do for a living and understands how it's actually done, it becomes a pretty rewarding thing to do, especially when someone at the top is world-class himself in terms of negotiating," Shay Assad, the Pentagon's pricing director, told attendees at a conference held by McAleese and Credit Suisse in March 2017, just two months after Trump's inauguration.

Assad had already built a reputation as the Department of Defense's toughest contract negotiator, having spent more than a decade battling defense companies on behalf of taxpayers, trying to get the prices down on skyrocketing weapons costs. Over the course of his career, he has been decorated with a panoply of awards from the Pentagon for his work, and praised for saving the government billions of dollars. A 2016 Politico profile described Assad, known for his dogged campaigns to force defense industry companies to justify their costs, as "the most hated man in the Pentagon."

Assad's aggressive approach to contract negotiations, however, paid off. The Pentagon credited the career civil servant with bringing down the costs of the Apache helicopter, the C-17 transport plane and the F/A-18 fighter, saving taxpayers more than half a billion dollars. And that wasn't all: A former senior Pentagon official said Assad had over the span of his career "saved the Department of Defense many billions of dollars."

Trump's interest in negotiating better prices for the government made it seem like Assad's work would get White House attention.

Yet within two years of Trump's entrance into the White House, Assad would find himself removed from his job, and his efforts to save money and recover hundreds of millions of dollars in potentially fraudulent spending tabled.

His treatment, he contends, was the direct result of his attempts to save the Pentagon money and identify potential contract fraud, which brought him into conflict with the Pentagon's top weapons buyer. It was a conflict that ended dramatically, he says, when shortly after he emailed senior Pentagon officials about potential fraud, details about his travel records and his demotion were published in the press.

Assad, who is now retired, says the issues he brought up involved potentially billions of dollars in waste and fraud, and still aren't being addressed. It's a claim that's backed up by multiple interviews conducted by Yahoo News with Assad and those who worked with him at the Pentagon, as well as by documents obtained through the Freedom of Information Act.