Final answer:
The author uses an Extended Metaphor in paragraph three to depict the potential drawbacks of foreign alliances, giving depth to the concept and adding clarity to the thematic concerns.
Step-by-step explanation:
The stylistic device the author uses in paragraph three to illustrate the potential ills of foreign alliances is an Extended Metaphor. An extended metaphor is a comparison between two unlike things that continues throughout a series of sentences in a paragraph or lines in a poem. It is often used to add depth, make something more relatable, or to help illustrate a broader theme or idea. In the context of the paragraph mentioned, the author employs this device to effectively convey complex concepts surrounding foreign alliances in a way that is both illustrative and impactful. The device helps to paint a vivid picture of the potential consequences and complexities of foreign entanglements.