Actual historical event which is the source of the legendary tale of Troy.
Historically, the Greeks, united under Agamemnon, captured the bulk of Asia Minor in 1184 BCE, and finally, the city of Troy.
The myth, Helen, the young wife of Agamemnon, deserts him for the younger Prince Paris of Troy. The myth revolves around the legendary torrid romance between Helen of Troy (“the face that launched a thousand ships”) and (Prince) Paris, heir to the throne of Troy. Note that Prince Paris got Helen, but lost everything else. Helen got Prince Paris, but effectively destroyed Troy.
That myth is combined with the myth of the Trojan Horse from the epic Latin poem The Aeneid. In the poem, after a fruitless 10–year siege of Troy, Greeks bearing gifts construct a huge figure of a horse on rollers and leave it at the gates of Troy (with Greek warriors hidden inside); the Greeks pretend to sail away; the Trojans wheel their new–found victory trophy inside; at night the Greek warriors slither out of the horse; they overpower the surprised gate–keepers of Troy from the inside, and manage to open the city gates; the Greeks who had secretly sailed back under cover of night, now finally gain entry to the city; Troy falls.