Only two American presidents have ever endured an impeachment trial: Andrew Johnson, and Bill Clinton. One other president, Richard M. Nixon, resigned from office before the terms of his impeachment could be drawn up.
Andrew Johnson was Abraham Lincoln's Vice President. After Lincoln was assassinated, Johnson became President. Those were strange times. Lincoln was a Republican. Johnson had been the only southern U.S. Senator who opposed the secession by the southern states which led to the Civil War. Johnson was a southern Democrat. He didn't have any major quibbles with slavery.
Tony Shaffer's publisher was all set to release his memoir when the Department of Defense stepped in and demanded that the entire first edition be destroyed. They pulped it.
This action was most unusual in light of the fact that Shaffer, a former US intelligence agent in Afghanistan, had previously obtained all the proper clearances to publish his book. The DOD then proceeded to censor significant portions of it. The book was eventually published in a heavily redacted version. Why is the DOD so worried about what Shaffer has to say?