Gatsby first meets Daisy in Louisville, Kentucky, while he is in military training before World War I.
At the time, Gatsby is a young officer stationed there, and Daisy is a wealthy, admired young woman from a prominent family. They fall deeply in love during this period, but their relationship is shaped by class differences from the start. Gatsby does not yet have the wealth or status to match Daisy’s world, even though he allows her to believe he belongs to her social class. When he leaves to fight in the war, their relationship is cut off, and Daisy eventually marries Tom Buchanan instead, choosing the security and status he offers.
This first meeting becomes the defining moment of Gatsby’s life. He spends the next several years trying to recreate that brief, intense past—building his fortune and even buying a mansion across the bay from Daisy, all to win her back. The fact that their relationship begins in a fleeting pre-war moment helps explain why Gatsby clings to it so obsessively: it exists for him as a perfect, untouched memory rather than a lived, evolving relationship. That tension between memory and reality drives much of the novel’s tragedy.