The Year of the Four Emperors is the label we attach to the 18-month period that opened with the suicide of Nero in June 68 and closed with the triumph of Vespasian in December 69. In the interim three other emperors held power, if only for a few months. There was Galba, officially declared emperor in June 68 and assassinated on 15 January 69. There was Otho, the man responsible for his murder. Having seized power by a coup in Rome, he committed suicide on 16 April, in the vain hope that his death would end the bloodshed. And there was Vitellius, hailed emperor by his troops on 3 January 69, recognized by the senate in Rome once they heard of Otho's death, and cut down by Vespasian's partisans on 20 December. Galba, Otho, Vitellius, and Vespasian were usurpers, of course, whereas Nero had been the legitimate emperor, the last male member of the Julio-Claudian dynasty established by Augustus a century earlier. In retrospect it is easy to make Vespasian's victory look inevitable. In fact, it owed an enormous amount to accident and luck. But Vespasian was a practical, hard-headed man, disinclined to look gifthorses in the mouth, and his dynasty, the Flavians, would rule the Roman world for 27 years.
Why write a book about all this, especially when, in the past century, there have been three full-length studies in English, by Henderson, Greenhalgh, and Wellesley? The answer revolves around the conflict between what the evidence says and the conclusions we can legitimately draw from it. It is a conflict that has bedeviled historians ever since the events took place. Tacitus, for example, our fullest source, had no qualms about denigrating his predecessors' works on the Year of the Four Emperors and the Flavian dynasty. Even as he plundered them for material, he asserted that they were all unreliable because written from a faulty perspective, and that the record needed to be set straight. One can still claim to be trying to set the record straight, since any new study of a period should rest on the proposition that previous works on the subject are flawed by shortcomings of some kind. It would be inexcusable as well as unjustifiable to dismiss the work of earlier scholars in the Tacitean