A trade war over history? Sort of. Why Japan and South Korea are feuding.

As nationalist sentiments rise around the world, Northeast Asia has not been immune. Propelled by decades-old resentments, Japan and South Korea are trading blows in a conflict that threatens to impact businesses around the world – and deepen divides between two allies the U.S. relies on to help counterbalance China and North Korea.

The trade spat kicked off with Tokyo imposing restrictions on chemicals key to South Korea’s high-tech industry, citing unspecified security concerns. Most observers, however, see the trade war as historical frictions spilling over into economic and national security arenas – underscoring how large the past looms in East Asia today.

How did all these tensions start?What is happening in the trade dispute?What is the United States doing – or not – to help smooth tensions?How does this reflect on U.S. diplomacy, more broadly?