Defender is the first and only scholarly biography of Daniel H. Wells, one of the important yet historically neglected leaders among the nineteenth-century Mormons-leaders like Heber C. Kimball, George Q. Cannon, and Jedediah M. Grant. An adult convert to the Mormon faith during the Mormons' Nauvoo period, Wells developed relationships with men at the highest levels of the church hierarchy, emigrated to Utah with the Mormon pioneers, and served in a series of influential posts in both church and state.

Wells was known especially as a military leader in both Nauvoo and Utah-he led the territorial militia in four Indian conflicts and a confrontation with the US Army (the Utah War). But he was also the territorial attorney general and obtained title to all the land in Salt Lake City from the federal government during his tenure as the mayor of Salt Lake City. He was Second Counselor to Brigham Young in the LDS Church's First Presidency and twice served as president of the Mormon European mission. Among these and other accomplishments, he ran businesses in lumbering, coal mining, manufacturing, and gas production; developed roads, ferries, railroads, and public buildings; and presided over a family of seven wives and thirty-seven children.

Wells witnessed and influenced a wide range of consequential events that shaped the culture, politics, and society of Utah in the latter half of the nineteenth century. Using research from relevant collections, sources in public records, references to Wells in the Joseph Smith papers, other contemporaneous journals and letters, and the writings of Brigham Young, Quentin Thomas Wells has created a serious and significant contribution to Mormon history scholarship.