Chapter 1 - War for Helen. From Trojan War: A New History, by Barry Strauss

Helen of Troy or Helen of Sparta, wife of King Menelaus, may have been drawn to the attentive Prince Priam of Troy. She may have gone willingly because Menelaus was oppressive, Paris good-looking, or because Anatolian women had more power than their Greek equivalents. Paris may not have been motivated so much by lust as by the desire for power, which he might gain by carrying "out a bloodless raid on enemy territory." Modern readers aren't the only ones skeptical of the love motive. However, by making the war a case of wife-stealing, Homer creates the sort of motive that suited the Bronze Age, when personal terms were preferred to abstracts. Troy had become an ally of the Hittites earlier in the century and could at that time count on protection. Priam probably didn't believe the Greeks would come to take back a missing queen and whatever possessions she took with her. Agamemnon would have had a hard task persuading the other Greek kings to join him in the risky war, but taking Troy meant plenty of plunder. Strauss says, "Helen was not the cause but merely the occasion of the war."

The Trojan War, by Barry Strauss