Hugo writes a bit about the role that weather played in the battle of Waterloo and how it unfolded. In this case, very specifically, he focuses on the fact that it rained, and as a result the cannons that Napoleon’s strategy were so dependent on could not be deployed until mid-morning, which meant that rather than the battle beginning around 6 am, hours before the allies of the opposing forces could arrive, it actually started around 11 am, giving the allies of Napoleon’s enemies plenty of time to reinforce and brace for the attack.
Where it seems that some have assumed that the loss of the battle was due to a deficiency on the part of Napoleon - perhaps an indicator of mental slippage or early signs of him beginning to verge on insanity - Hugo posits that this is really about factors beyond Napoleon’s control. Weather created hazards that shaped the events of the day and led to Napoleon’s demise. Was it fate? Was it destiny of some sort? These are the questions Hugo teases as he begins to unfold his retelling of the battle of Waterloo, something he assures us has direct relevance to at least one character important to our story.