Personification heightens the reader's awareness in The War of the Worlds of the emotional and psychological impact of an alien invasion. In Book 1, Chapter 14, the narrator personifies London as someone who goes to bed oblivious and wakes up in terror:
It was the dawn of the great panic. London, which had gone to bed on Sunday night oblivious and inert, was awakened in the small hours of Monday morning to a vivid sense of danger.
Here, the narrator describes London as someone who "had gone to bed" peacefully and "awakened [...] to a vivid sense of danger." This passage provides a powerful example of personification because it treats the city of London as if it were a person. The city is filled with people who feel similarly about the Martian invasion, and the passage makes it seem like the same thing happens to every single inhabitant. Thus, personification helps heighten the story's sense of emotion by describing the widespread terror of invasion across an entire city.
Note that this is also an example of synecdoche, a figure of speech in which a part is made to represent a whole (or vice versa). In this case, London represents its inhabitants. This passage minimizes the importance of individual people by emphasizing the city's collective panic instead of focusing on individual reactions to the invasion.