Tensions between Japan and South Korea spiked on Friday when Tokyo recalled its ambassador over a statue of a "comfort woman". Japan recalled its ambassador to South Korea to protest the placing of a statue symbolising victims of Japanese wartime sex slavery outside its consulate in the city of Busan last month.
In a move likely to reignite a feud over the "comfort women" issue, Japan's chief government spokesman Yoshihide Suga also announced that Japan is ordering home its consul-general in Busan and suspending discussions over a Japan-South Korea currency swap.
The plight of the women is a hugely emotional issue that has marred relations between the two Asian neighbours for decades and which, for many South Koreans, symbolises the abuses of Japan's 1910-45 colonial rule over the Korean peninsula.
The move marks the latest development in an ulcerative dispute over Japan's wartime system of sex slavery that has roiled relations for decades. It has also proven a diplomatic headache for the United States, which wants to strengthen security cooperation between Tokyo and Seoul.
Here are some key questions about the issue:
The term, a euphemism for sex slaves, refers to women and young girls mostly from the Korean peninsula, China, the Philippines and what is now Indonesia, who were taken to former Japanese military installations and forced to provide sex to officers and soldiers during World War II.
Up to 200,000 women are believed to have been sexually enslaved by Japan during the war, though estimates range higher and lower. Few survive 70 years after the end of the war.
A majority of Japanese feel they have atoned enough for the country's wartime aggression and other wrongdoing, including the comfort women issue, after numerous apologies. But many South Koreans and Chinese question the sincerity of the apologies and point to statements and actions by Japanese leaders, including the visit late last month to a war shrine in Tokyo by Japan's hawkish defence minister.
At the end of 2015, Japan announced it was offering a $8.6m payment for survivors and an apology from nationalist Prime Minister Shinzo Abe. Both sides agreed that this represented a "final and irreversible," settlement. But some activists in South Korea dispute this and demand a more fullsome apology and greater compensation.
Campaigners installed a bronze statue of a "comfort woman" outside the Japanese consulate in Busan, a copy of one that sits outside their Seoul embassy, but it was removed after the governments reached their settlement.
But after the Japanese defence minister paid homage at Yasukuni Shrine last month, a spot where senior convicted war criminals are honoured, Seoul allowed the activists to put the statue back up.