Why Thucydides Trap is trending

<p>Chinese President Xi Jinping used the term "Thucydides Trap" during his summit with President Donald Trump on Thursday. CNN's Betsy Klein breaks down the political theory based on ancient Greece and explains what Xi meant when he referenced it. Discover more videos, including live streams and exclusive storytelling, on our <a href="https://www.cnn.com/watch">Watch</a> page.</p>