"Justinian’s reign also saw an outbreak of plague, and much of the Eastern Empire was to fall in to Arab hands in the 630s. The suggestion is often raised, therefore, that the plague and conquests had between them overstretched imperial resources." I read this in a book on European history, and here the author is talking about the Byzantine Empire. I'm not quite sure what does "had between them..." mean? Does it mean that a) there is some kind of relation between the plague and the conquests (which is the overstretched imperial resources) or b) both the plague and conquests have resulted in overstretched imperial resources? or something else? Thanks for answering!