President Barack Obama has become the first sitting US president to visit the western Japanese city of Hiroshima, the site of the first atomic bombing at the end of World War II in 1945.
Friday's visit - the culmination of Obama's nuclear policy since he made a landmark speech on his vision for a nuclear-free world in Prague in 2009 - has stirred another round of decades-long controversy in Japan and the US over the legitimacy and necessity of the bombings of Hiroshima on August 6, 1945, and Nagasaki three days later.
Obama's visit is also a source of concern for Japan's neighbours, particularly South Korea and China, for different reasons.
China and South Korea fear Japan's nationalists would avail themselves of this opportunity to whitewash Tokyo's wartime atrocities, committed in the first half of the 20th century, and shake off its image as an aggressor.
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To say nothing of the often fierce, present-day territorial rows between Asian neighbours and Japan, the shared troubled history still haunts Northeast Asia, and is a major stumbling block to dialogue and cooperation in the region.
China and South Korea still vividly remember Japan's wartime atrocities, most notably the Nanking Massacre in 1937, in which as many 300,000 Chinese civilians and disarmed combatants are estimated to have been killed by Japanese troops.
Meanwhile, up to 200,000 "comfort women" - many from Korea - are believed to have been forced into sex slavery in Japan's wartime brothels.
They feel that Tokyo's past offers of apologies have been insufficient and insincere, as such words of atonement have often been contradicted by actual deeds by prominent politicians, who often visit the controversial Yasukuni shrine that honours Japan's A-class war criminals.
School textbooks have also been revised to put a positive light on Japan's wartime history, and attempts made to change the country's pacifist constitution that outlaws war as a means to settle international disputes.
Japan's conservatives think that enough time has passed and the next generation shouldn't feel the burden of its history.
Obama made it clear in his interview with Japan's public broadcaster NHK that he would not offer an apology and Japan also said it would not seek one.
However, in the eyes of many ordinary people around the world, the powerful and symbolic picture of him laying a wreath at the cenotaph of the Hiroshima Peace Memorial Park - dedicated to the victims of the atomic bomb in Hiroshima that killed about 140,000 people in 1945 - could be construed as one, potentially diluting Japan's image as a wartime aggressor.
Hong Lei, China's foreign ministry spokesman, voiced concerns in a rather measured tone, saying: "We hope that by inviting leaders or political figures of other countries to visit Hiroshima, Japan is telling the world that it will never tread on the path of militarism again, as it once brought unspeakable suffering to its people and people of Asia."
In an open letter to Obama, a group of civic organisations in South Korea called for him to ensure his visit doesn't end up justifying Japan's wartime crimes, or expand Tokyo's role militarily in world affairs.
Members of the Korean Victims' Association of the Atomic Bombings are planning to visit Hiroshima and deliver a letter to Obama, calling for a sincere apology and reparations both from the governments of the US and Japan.
As many as 40,000 Koreans - most of whom were forced to work in Japan during its colonial rule over the Korean peninsula - were killed and another 30,000 exposed to radiation from the atomic bombings of Hiroshima and Nagasaki.
Despite such wary eyes, however, with Japan being a strategic partner for the Obama administration's "rebalancing" policy vis-a-vis the Asia Pacific region, this visit is likely to help further expand Japan's military contribution to the ever-closer Japan-US alliance in the face of an increasingly assertive China.
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Source: Al Jazeera