I agree that the political, or I suppose sectional, context is important to understanding the exchange, but I think the thing that strikes me most about it is that, ignoring the specifics about forts and cannon and so on, it is a sort of exchange immediately familiar to almost anyone who’s had a boss before. The specific context in which a modern reader would encounter the exchange is in study of the attack on Fort Sumter and the American Civil War which followed. Weighty stuff. But Floyd’s query also kinda reads like an email you might get from your boss about that deadline that got slipped. Plus ça change, plus c’est la même chose and all that.
But while we’re on the subject of the broader historical context, it’s probably worth noting that Floyd would later be a general in the Confederate Army and approximately two years after the exchange reproduced above would himself be responsible for the defense of a fort, in this case Fort Donelson. The failed defense of which led to Floyd to abandon his post—leaving a subordinate to surrender it—and fleeing under the cover of night for fear of being hanged for a traitor if captured. The successful attack on Fort Donelson is one of the actions that established the reputation of Floyd’s opposite on the Union side, then general and future president U.S. Grant.