They are called "comfort women" by Japan, a polite euphemism that hardly reflects what they went through. In reality, the estimated tens of thousands of young girls who were forced to copulate with Japanese soldiers and officers during World War II in China, the Korean peninsula, the Philippines and other parts of Asia can be more accurately described as "sex slaves". But on his historic visit to Washington this week, Japanese Prime Minister Shinzo Abe barely touched the subject, fanning the flames of a controversy that dogs his administration at every turn and underpins much of its negotiations with its Asian neighbours.

As Abe became the first Japanese Prime Minister to address a joint session of the US Congress on Wednesday, protesters demanded a formal, unequivocal apology to the so-called comfort women, some of whom are still alive. During a joint press conference with US President Barack Obama on Tuesday, Abe reiterated his support for the "Kono" statement, a 1993 acknowledgement and apology that "comfort stations" existed and that women were coerced into participating. But he stopped short of making a new apology and completely ignored the subject in his speech to lawmakers.

That disappointed many people, particularly the victims themselves, who argue Abe's words aren't enough and any previous apology lacks the teeth for victims to make claims against Japan in courts for compensation. "I don't expect him to change overnight," Yong Soo Lee, an 86-year old Korean survivor who attended the Congressional speech, told DC Dispatches.

The Obama administration has danced around the topic in the week leading up to the visit but one analyst said officials are frustrated with Japan's lack of progress on the issue. "Prime Minister Abe is needlessly providing ammunition to his critics in China and South Korea," said Sue Mi Terry, a former US intelligence officer who specialises in Asian affairs. She added Abe is "creating an obstacle to Japan's further normalising its military and rearmament by flirting with historical revisionism".

Meanwhile, a group of lawmakers, led by California Congressman Mike Honda, have called on Abe to "squarely face history" with its Asian neighbours by not only apologising but also updating history textbooks in Japan to reflect the reality of what the women went through. Honda called Abe's decision not to mention the issue in his speech "utterly shameful and shocking".

Source: Al Jazeera