Japan and South Korea have long-established themselves as fervent allies of the United States, but recent altercations between the two Pacific nations have shown that the friend of a friend can still be your enemy.

On Wednesday, South Korean officials accused a Japanese military patrol aircraft of executing a “threatening” low-altitude pass over one of their destroyers as it sailed through international waters. This incident and the ensuing diplomatic fallout is just the latest spat between the two nations following a December incident in which Japanese officials claimed a South Korean vessel locked onto a Japanese aircraft with its fire control radar. The Japanese plane was reportedly involved in rescue operations for a North Korean fishing boat at the time of the incident, but Seoul claimed the aircraft flew dangerously close to its ship. South Korean officials have also claimed that the use of radar was not meant as a provocation, but that it had been activated to assist in searching for the fishing boat.

Both nations, as a result, have demanded apologies from one another.

According to General Suh Wook, the chief director of operations for South Korea’s Joint Chiefs of Staff, Wednesday’s low flyover was the third time a Japanese patrol aircraft buzzed a South Korean Navy vessel. He went on to warn that his nation’s military will respond if provoked.