Even after WW2, the U.S. Army used Recreation and Amusement Association that employed more than 50,000 prostitutes in Japan. They were official institution supported by Japanese goverment.
The U.S. Army employed many prostitutes in the Korean War and the Vietnam War. According to Against Our Will: Men, Women, and Rape, Peter Arnett, a respected journalist who reported the Vietnam War testified as follows:
By 1966, official military brothels had been established within each division’s camp. Each one was a two-building “recreation area” where 60 Vietnamese women lived and worked. The prostitutes decorated their cubicles with nude photographs from Playboy magazine and had silicone injected into their breasts to make the American soldiers feel more at home.Arnett said that these "recreation areas" were authorized by the Chief of Staff and the Defense Department. He estimated that more than 300,000 prostitutes worked during the Vietnam War.
They were neither kidnapped by the Army nor sold by human trafficking, but it was not only Japanese Army that employed prostitutes in the battle field. Let him who is without sin cast the first stone.