Survivors and victims of Nanjing Massacre attend a ceremony to mourn the Nanjing Massacre victims at the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders on the Qingming Festival in Nanjing, capital of east China's Jiangsu Province, April 4, 2016. Japanese troops captured Nanjing, then China's capital, on Dec. 13 of 1937 and started a 40-odd-day slaughter. More than 300,000 Chinese soldiers who had laid down their arms and civilians were murdered, and over 20,000 women were raped. (Xinhua/Han Yuqing)

Survivors of Nanjing Massacre Xiang Yuansong speaks in a ceremony to mourn the Nanjing Massacre victims in front of a wall inscribed the name list of victims at the Memorial Hall of the Victims in Nanjing Massacre by ese Invaders on the Qingming Festival in Nanjing, capital of east China's Jiangsu Province, April 4, 2016. Japanese troops captured Nanjing, then China's capital, on Dec. 13 of 1937 and started a 40-odd-day slaughter. More than 300,000 Chinese soldiers who had laid down their arms and civilians were murdered, and over 20,000 women were raped. (Xinhua/Sun Can)

Survivor of Nanjing Massacre Yang Cuiying offers flowers to passed relatives in a ceremony to mourn the Nanjing Massacre victims at the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders on the Qingming Festival in Nanjing, capital of east China's Jiangsu Province, April 4, 2016. Japanese troops captured Nanjing, then China's capital, on Dec. 13 of 1937 and started a 40-odd-day slaughter. More than 300,000 Chinese soldiers who had laid down their arms and civilians were murdered, and over 20,000 women were raped. (Xinhua/Han Yuqing)

Survivors and victims of Nanjing Massacre stand in silent tribute in a ceremony to mourn the Nanjing Massacre victims in front of a wall inscribed the name list of victims at the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders on the Qingming Festival in Nanjing, capital of east China's Jiangsu Province, April 4, 2016. Japanese troops captured Nanjing, then China's capital, on Dec. 13 of 1937 and started a 40-odd-day slaughter. More than 300,000 Chinese soldiers who had laid down their arms and civilians were murdered, and over 20,000 women were raped. (Xinhua/Sun Can)

A ceremony to mourn the Nanjing Massacre victims in front of a wall inscribed the name list of victims is held at the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders on the Qingming Festival in Nanjing, capital of east China's Jiangsu Province, April 4, 2016. Japanese troops captured Nanjing, then China's capital, on Dec. 13 of 1937 and started a 40-odd-day slaughter. More than 300,000 Chinese soldiers who had laid down their arms and civilians were murdered, and over 20,000 women were raped. (Xinhua/Han Yuqing)

Tamaki Matsuoka (L), head of the Japan-China Peace Research Organization, talks with survivor of Nanjing Massacre Yang Cuiying in a ceremony to mourn the Nanjing Massacre victims at the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders on the Qingming Festival in Nanjing, capital of east China's Jiangsu Province, April 4, 2016. Japanese troops captured Nanjing, then China's capital, on Dec. 13 of 1937 and started a 40-odd-day slaughter. More than 300,000 Chinese soldiers who had laid down their arms and civilians were murdered, and over 20,000 women were raped. (Xinhua/Han Yuqing)

Children chorus sing a song in a ceremony to mourn the Nanjing Massacre victims at the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders on the Qingming Festival in Nanjing, capital of east China's Jiangsu Province, April 4, 2016. Japanese troops captured Nanjing, then China's capital, on Dec. 13 of 1937 and started a 40-odd-day slaughter. More than 300,000 Chinese soldiers who had laid down their arms and civilians were murdered, and over 20,000 women were raped. (Xinhua/Sun Can)

Tamaki Matsuoka, head of the Japan-China Peace Research Organization, speaks in a ceremony to mourn the Nanjing Massacre victims at the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders on the Qingming Festival in Nanjing, capital of east China's Jiangsu Province, April 4, 2016. Japanese troops captured Nanjing, then China's capital, on Dec. 13 of 1937 and started a 40-odd-day slaughter. More than 300,000 Chinese soldiers who had laid down their arms and civilians were murdered, and over 20,000 women were raped. (Xinhua/Sun Can)

Survivors of Nanjing Massacre attend a ceremony to mourn the Nanjing Massacre victims at the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders on the Qingming Festival in Nanjing, capital of east China's Jiangsu Province, April 4, 2016. Japanese troops captured Nanjing, then China's capital, on Dec. 13 of 1937 and started a 40-odd-day slaughter. More than 300,000 Chinese soldiers who had laid down their arms and civilians were murdered, and over 20,000 women were raped. (Xinhua/Han Yuqing)

Survivor of Nanjing Massacre Yang Cuiying offers flowers to victims in a ceremony to mourn the Nanjing Massacre victims at the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders on the Qingming Festival in Nanjing, capital of east China's Jiangsu Province, April 4, 2016. Japanese troops captured Nanjing, then China's capital, on Dec. 13 of 1937 and started a 40-odd-day slaughter. More than 300,000 Chinese soldiers who had laid down their arms and civilians were murdered, and over 20,000 women were raped. (Xinhua/Sun Can) 10