Junius was the pseudonym of a writer who contributed a series of letters to the Public Advertiser, from 21 January 1769 to 21 January 1772. The signature had been already used, apparently by him, in a letter of 21 November 1768. These and numerous other personal letters were not included in his Letters of Junius collection, published in 1772.
The name may have been chosen because the same author had already signed Lucius and Brutus, and wished to exhaust the name of Lucius Junius Brutus, the Roman patriot who led the overthrow of the Roman monarchy. Alternatively, the name may have been derived from the Roman poet Juvenal, who was thought also to have had the nomen Junius. Some say that the author of the Junius letters had previously written under numerous other pseudonyms, and that he continued to do so, under different pseudonyms, after the 36-month period (January 1769 – January 1772) in which the Junius letters were published. He may, for example, have written as Philo-Junius, a character who came to the rescue of Junius when it was clear that the public was misinterpreting his messages. There is weak evidence that he also wrote as Veteran, Nemesis and other anonymous correspondents published in the Public Advertiser.
There is a marked distinction between the main Letters of Junius, intended for the erudite public, and his miscellaneous letters. The second deal with a variety of subjects, some of a purely personal nature, such as the alleged injustice of the Viscount Barrington, the secretary at war, to the officials of his department.
The Letters of Junius had a definite objective:
Foremost in his sights was the ministry of Augustus Henry Fitzroy, 3rd Duke of Grafton, a fellow Whig whom Junius viewed as particularly corrupt. Grafton's administration had been formed in October 1768, when William Pitt the Elder was compelled by ill health to retire from office, and was a reconstruction of his cabinet of July 1766. Junius fought for the return to power of Pitt, who had recovered and was not on good terms with his successors.