At a combined 34,833 lines, John Lydgate's Troy Book (1412–1420) and Siege of Thebes (c. 1422) rank as two of the lengthiest and most ambitious works of Lydgate's massive literary output. Although they have received a relatively large amount of critical attention from scholars, debate has tended to focus on two related issues. First, critics have attempted to determine how far Lydgate was complicit with the agendas of his patron, Henry V and, in the case of Siege of Thebes, seemingly written without a specific commission, with the ideologies and strategies of the ‘Lancastrians’ more generally; and second, criticism has centred on the degree to which Troy Book and Siege of Thebes can be seen to support or critique Henry's wars in, and policies towards, France.

For Paul Strohm, for example, Lydgate ‘sought consistently to advance Henry's prospects, first as Prince and then as King Henry V, as well as those of his infant son’ and he argues for the ‘complete identification’ of the Siege of Thebes ‘with Henry V's ambitions in France’. Strohm characterises both Lydgate and his contemporary Thomas Hoccleve as attempting to be ‘as complicit as possible in every aspect of the Lancastrian program’. For James Simpson, on the other hand, Lydgate ‘was not by any means a propagandist poet’; rather, his Troy Book and Siege of Thebes are ‘consistently anti-imperialistic’. According to Simpson, the Siege of Thebes ‘offers an extremely powerful admonition against lightly taking on war, whether civil or against France, whatever the perceived justice of the cause’.