The father of the billionaires Charles G. and David H. Koch helped construct a major oil refinery in Nazi Germany that was personally approved by Adolf Hitler, according to a new history of the Kochs and other wealthy families.

The book, "Dark Money," by Jane Mayer, traces the rise of the modern conservative movement through the activism and money of a handful of rich donors: among them Richard Mellon Scaife, an heir to the Mellon banking fortune, and Harry and Lynde Bradley, brothers who became wealthy in part from military contracts but poured millions into anti-government philanthropy.

But the book is largely focused on the Koch family, stretching back to its involvement in the far-right John Birch Society and the political and business activities of the father, Fred C. Koch, who found some of his earliest business success overseas in the years leading up to World War II. One venture was a partnership with the American Nazi sympathizer William Rhodes Davis, who, according to Ms. Mayer, hired Mr. Koch to help build the third-largest oil refinery in the Third Reich, a critical industrial cog in Hitler's war machine.

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David H. Koch, left, and Charles G. Koch. Credit Paul Vernon/Associated Press; Bo Rader/The Wichita Eagle, via Associated Press

The episode is not mentioned in an online history published by Koch Industries, the company that Mr. Koch later founded and passed on to his sons.

Ken Spain, a spokesman for Koch Industries, said company officials had declined to participate in Ms. Mayer's book and had not yet read it.

"If the content of the book is reflective of Ms. Mayer's previous reporting of the Koch family, Koch Industries or Charles's and David's political involvement, then we expect to have deep disagreements and strong objections to her interpretation of the facts and their sourcing," Mr. Spain said.