Why a military spat between Japan and South Korea could snowball into crisis

A photograph released by the South Korean Defense Ministry appears to show a Japanese plane as seen on board one of its destroyers, the Dae Joyeong, on Wednesday.

(CNN)Japan and South Korea are engaged in a heated military dispute that analysts say could damage the already tenuous geopolitical situation in northeast Asia if the two sides do not reach a resolution.

The spat began December 20 after an encounter between a Japanese plane, which Tokyo said was collecting intelligence, and a South Korean destroyer, which Seoul said was on a humanitarian mission.
Both sides disagree on what happened next -- the Japanese said the South Koreans targeted their aircraft with missile-targeting radar, while the South Koreans said the Japanese plane was flying dangerously low and that the radar "was not intended to trace any Japanese-controlled aircraft."
    The disagreement has quickly escalated, bringing to the fore historical disputes previously on the back-burner and -- in turn -- threatening the region's stability.
    "East Asian geopolitics has been shaken loose and is now unsettled," said Van Jackson, a former US Department of Defense official specializing in the Asia-Pacific.
    "China is seeking to push out the US, North Korea has pulled a jiujitsu move by using summit diplomacy to solidify its status as a nuclear state even as the ostensible purpose is to denuclearize Pyongyang, and the future of the US in the region is less certain now than any time since the 1970s.
    "Amid all this tumult, suppressed animosities are started to crack through the veneer of regional stability."

    A marriage of convenience

    South Korea and Japan are historical adversaries locked in a marriage of convenience, which makes for a complex partnership. Their relationship is still very much colored by the legacy of imperial Japan's occupation and colonization of the Korean Peninsula in the first half of the 20th century.
    This revived tension comes at a terrible time for the United States -- the Trump administration is currently preparing for its second summit with North Korea, while also inching towards a key deadline in trade talks with China.
    Shortly after the initial incident, Japan and South Korea held working-level meetings to try to resolve the issue behind closed doors.
    It appears to not have worked -- and neither side is buying the other's explanation.
    Japan released video of the incident from its perspective on December 28. South Korea released its own video on January 4. Each accused the other of misleading the public and distorting the facts.
    Japan has conducted three other flybys over South Korean ships this month -- one last week, one on Tuesday and another Wednesday. Seoul publicly condemned the latest as a "clearly provocative act" against a "partner country."
    South Korea's Defense Ministry released this radar photo, which it says shows a Japanese patrol aircraft 7.5 kilometers (4.6 miles) away from the South Korean naval destroyer Dae Joyeong.
    Lawmaker Song Young-gil, from South Korea's ruling Democratic Party, has even gone so far as to suggest Seoul pull out of its General Security of Military Information Agreement, a pact allowing the two countries to share sensitive intelligence.
    Jonathan Berkshire Miller, an analyst at the Tokyo-based Japan Institute for International Affairs, believes historical enmity contributed to the sudden deterioration of relations.
    "The context is key," he said.

    Historical adversaries

    Despite their historical differences, South Korea and Japan share plenty of surface similarities. They're both vibrant democracies with developed economies. Geopolitically, they are both US allies; they both want a denuclearized North Korea; they both support free trade; and they both view China's rise with trepidation.
    But history looms large, and the Japanese occupation and colonization of Korea -- when many Koreans were brutalized, murdered and enslaved -- is still a highly emotional issue that defines their relationship.
    South Korea and Japan signed a treaty in 1965 that normalized relations between the two countries and was supposed to settle most of the wartime issues.