An international outcry has flared again after members of the U.S. House of Representatives submitted a resolution in January urging Japan to formally apologize for forcing young females across Asia into sexual slavery during the war.

Prime Minister Shinzo Abe has repeatedly said he stands by the government's 1993 statement of apology to the "comfort women" that admitted the Imperial forces' involvement -- directly and indirectly via agents -- in forcing young females into frontline brothels. But Abe also claimed no official document ever surfaced to prove the military coerced them.

Leading historians with conflicting views -- Ikuhiko Hata, a lecturer at Nihon University who denies there were any sex slaves, and Yoshiaki Yoshimi, a Chuo University professor who played a central role in bringing the dark episode in Japan's history out into the open, offer the following: