In Night Watch, Sub-Lieutenant Harrap is the extremely unlucky, extremely junior, officer despatched first to the Palace to inform Winder that there has been no luck in smashing the Republic of Treacle Mine Road. On the not-long-delayed death of Winder, his senior officers gleefully despatch him on another bum assignment: to go out and negotiate with the rebels following one final action which has resulted in the deaths of several of them, including Horace Nancyball.
As Major Clive Mountjoy-Standish and Captain Tom Wrangle explicitly wanted a junior officer for this duty who "has been a bit slack lately", the luckless Harrap must have been more than noticeably remiss in his duties... Harrap brings the news to Samuel Vimes that Winder is dead and Snapcase has been elected as Patrician, thus ending the civil war and bringing the first news of an amnesty for the rebels.
The social structure and military rank system of Ankh-Morpork is very closely based on that prevailing in Great Britain. For instance, John Keel is a sergeant-at-arms - a uniquely British military rank - rather than its American equivalent of Top Sergeant (the one we know from Sergeant Bilko, where the rank badge is a diamond shape with upward and downward pointing chevrons). In the British military rank system, a Sub-Lieutenant is the second-lowest form of commissioned rank, not in the Army but in the Royal Navy. So a lone sailor so far from a ship must have been luckless, friendless, and fair game for all the dirty work going...