What is the main conflict in The Left Hand of Darkness by Ursula K. Le Guin?

The basic principle of The Left Hand of Darkness is one that started in Ursula K. Le Guin's first novel in 1966 and runs through several of her early works: that of the interplanetary expansion started by the first race of humanity on the planet Hain and expanded across the universe, forming the League of All Worlds, eventually expanding to the eightythree-world collective called the Ekumen. This novel takes place in the year 4870 and concerns an envoy, Genly Ai, who is on a planet called Winter ("Gethen" in the language of its own people) to convince the citizens to join the Ekumen. Winter is, as its name indicates, a planet that is always cold, and its citizens are neither female nor male: they only have gender identities or sexual urges once a month. These conditions have affected the ways that civilizations on Winter have developed, with the most obvious effect being that there has never been a war on the planet.