Manlius first held the "imperium" in 405 BC as one of six consular tribunes. His colleagues in the office were Titus Quinctius Capitolinus Barbatus, Quintus Quintius Cincinnatus, Gaius Julius Iulus, Lucius Furius Medullinus and Manius Aemilius Mamercinus; Manlius was the only newcomer to the "imperium", as all of his colleagues were "consulares", the college was also unique in that it was the first year there were six consular tribunes. This year saw the beginning of the long and drawn out Siege of Veii. Diodorus has Mamilius instead of Manlius as consular tribune and only has the college consist of three members this year, which is believed to be a mistake by the ancient historian or by later transcribers. There is some doubt among modern scholars in regards to the historicity of these consular colleges of six and there are indications of a higher degree of interpolation during this period.