Eighty-five years ago, in the heart of North China, in what is now Yangquan in Shanxi province, was the epicenter of one of the most significant campaigns in the Chinese People's War of Resistance Against Japanese Aggression (1931-45).

Known as the Hundred Regiments Offensive, the campaign was a bold and unprecedented counterattack by the Eighth Route Army, led by the Communist Party of China, that not only disrupted enemy operations but galvanized national morale during the darkest days of World War II.

Launched on the night of Aug 20, 1940, the operation involved an astonishing 105 regiments — hence its later name — and continued for over five months, ending in January 1941.

Over the course of 1,824 engagements, the offensive inflicted more than 20,000 Japanese casualties. It was the largest and longest strategic offensive carried out by the Eighth Route Army in North China during the war.

"This battle was originally focused on sabotaging the Zhengding-Taiyuan Railway, but the scale quickly expanded," says Li Qi, a docent at the Hundred Regiments Offensive Memorial Hall in Yangquan. "It evolved into a large coordinated attack across multiple fronts, drawing in more than 100 regiments. That's how it earned its name."

The offensive paralyzed the 243-kilometer railway — a vital line connecting Zhengding in Hebei province with Taiyuan in Shanxi — which the Japanese army relied heavily upon for troop and supply transport.

"At 8 pm that night, with the firing of signal flares from the Eighth Route Army headquarters, troops and civilians began attacking key points along the railway," Li says.