Japan withdrew on Friday from an international naval review scheduled for next week because South Korea asked that Japan not fly the “Rising Sun” flag on its ships. The Koreans see the flag as symbolic of Imperial Japan’s atrocities in World War II, but Japan said its ships are required by law to fly it.

The event next week is not a military exercise, but a fleet review, essentially a seagoing parade intended to demonstrate international unity. The United States and China are among the invited participants.

Japan participated in similar events in 1998 and 2008 with its ships flying the Rising Sun ensign or kyokujitsuki, employed by many units of the Japanese Self-Defense Force since the 1950s.

South Korea, as host of the 2018 review, asked all 14 participating countries to fly only their own national flag and the flag of South Korea. The South Koreans voiced particular objections to the kyokujitsuki, likening it to Nazi German’s swastika as a symbol of evil from World War II and a memento of Japan’s brutal occupation of the Korean peninsula. Seoul employed diplomatic channels to ask Japan to “consider the public sentiment our people have over the Rising Sun flag.”

The political backdrop to the flag controversy is a recent significant worsening of relations between Japan and South Korea over the issue of Korean “comfort women” forced into sexual slavery by Imperial Japan in the war. Japan considered the matter settled by an agreement reached with the previous South Korean administration, but current President Moon Jae-in alarmed Tokyo by shutting down a foundation that was a key element of the settlement. Moon and Japanese Prime Minister Shinzo Abe had an unpleasant discussion of the matter on the sidelines of the U.N. General Assembly in New York last week.

Japan’s chief of staff, Katsutoshi Kawano, rejected the South Korean request on Thursday, insisting the Rising Sun ensign is a symbol of “pride” for the Maritime Self-Defense Force and stating, “We absolutely do not go if we have to remove the flag.”

“When it comes to the Maritime Self-Defence Force ensign, domestic laws and regulations stipulate that it must be hoisted at the stern. Regrettably, we have reached a decision that we cannot help forgoing the participation,” Japanese Defense Minister Takeshi Iwaya announced on Friday.

Iwaya noted that Japanese law requires displaying the flag and contended it has been so long identified with Japan’s military forces that striking it would be contrary to maritime law and tradition. Easily recognized flags for warships have long been considered both a proud tradition and a practical necessity on the high seas, although presumably no one involved in the fleet review next week would fail to recognize Japan’s ships without it.

North Korea naturally had to get involved in the discussion. “The ‘Rising Sun’ flag is a war-crime flag that the 20th-century Japanese imperialists used when executing their barbaric invasions into our nation and other Asian nations. Planning to enter flying the ‘Rising Sun’ flag is an unbearable insult and ridicule to our people,” a state-run North Korean website declared on Friday.