As relations between Beijing and Tokyo plumb a new low, the descendants of hundreds of Chinese men forced to work in wartime Japan are taking big, modern-day Japanese corporations to court, seeking millions in compensation.

Japan invaded China in 1937 and ruled parts of it with a brutal hand for the next eight years. Chinese historians say nearly 40,000 men were taken to Japan against their will to work in mines and construction. Survivors say living conditions were appalling. Many did not make it back to China.

In possibly the biggest class-action suit in Chinese legal history, about 700 plaintiffs lodged a case against two Japanese firms at a courthouse in eastern Shandong province in April, according to Fu Qiang, a lawyer representing the families. Among the plaintiffs are several forced laborers now in their 80s and 90s, and this might be their last chance to seek redress.