A week before Germany attacked the Soviet Union on June 22, 1941, the Communist Party of China Central Committee warned Josef Stalin the attack was imminent.
The CPC also gave the Soviets details of the Japanese Kwantung Army deployment in northeast China before Soviet forces made a final strike on the crack Japanese troops.
Yan Baohang, a senior adviser to General Chang Hsueh-liang, gathered the intelligence and sent it to the Soviet Union via conduits of the CPC.
Yan Mingfu, Yan Baohang's son and the former head of the  United Front Work Department of the CPC Central Committee, recalled his father's activities in a recent interview.
In spring 1941, Zhou Enlai, CPC chief representative to Chongqing, the wartime capital of the Republic of China, ordered Yan Baohang, who was also a CPC member but was posing as a democracy advocate, to gather intelligence for the CPC and the Communist International.
"My father had extensive high-profile networks, including almost all the important men within the government," Yan Mingfu said, adding that his father knew Madame Chiang Kai-shek, Sun Ke, son of Dr Sun Yat-sen, and Yu Youren, a veteran statesman of the Chinese Kuomintang Party.
In May 1941, Yan Baohang was invited to a banquet for the German military attache and learned Germany planned to invade the Soviet Union on  June 20.
During toasts, Yan heard Yu talking about the possible German strike, which was confirmed by Sun.
Yan left the banquet and reported to Zhou, who sent a telegram to Yan'an, wartime headquarters of the CPC and its military forces. On June 16, the CPC telegrammed the intelligence to Moscow.
The Soviets hastened preparations and avoided even greater losses to the invading Germans.
In 1944, Chen Cheng, head of the political department of the government's military committee, told Yan to research whether Japan would invade the Soviet Union in the closing months of World War II.
Yan "borrowed" from one of his countrymen the highly classified files on the deployment of the Japanese Kwantung Army in northeast China.
The files included the deployment, fortresses, defense plans, weapons, size of units and names of all generals.
With this vital intelligence, the Soviet army overturned the Japanese forces in a matter of days in August 1944.
Born in April 1895 in Haicheng, Liaoning Province, Yan was respected in the northeast for disobedience of Japanese occupation in the 1930s.