[5] The Northeast Anti-Japanese United Army conducted a protracted campaign which threatened the stability of the Manchukuo regime and the Japanese colonial rule, especially during 1936 and 1937.

Lacking the troops and materiel to conduct full-scale conventional warfare, the army's strategies were primarily to form pockets of resistance in occupied areas to harass the Japanese troops and undermine their attempts at local administration, and to launch small surprise attacks to divert resources from Japan's advance into China proper or against the Soviet Union after the border clashes of Chengkufeng (1938) and Battle of Khalkhin Gol (1939).

[citation needed] Yang twice commanded western marches that threatened Japanese lines of communication to Tieling and Fushun in Liaoning Province.

From the latter half of 1938, Japan concentrated large numbers of its troops in Manchukuo with the mission of encircling Yang's army and placed a 10,000-yuan bounty on his head.

[citation needed] By 1940, the war was stalemated although Japan held most of the Manchurian coastal areas and the open country along the railroads, small forces of Chinese guerrillas fought doggedly on from the mountains and woodlands.

In response, the Japanese committed a scorched earth strategy by routinely looting rural harvests, confiscating food from villages, and forcefully segregating civilians into "lawful settlements," in an attempt to deprive the resistance of any means of supply.

He was eventually cornered in a small forest by a large combined Japanese and collaborationist forces in the Mengjiang County (蒙江县), and was killed during fierce fighting by multiple shots from machineguns.

When they cut open Yang's stomach, they found only tree bark, cotton batting and grass roots within—not a single grain of rice.

Panicked, Kishitani ordered his men to rebury the body properly with full cemetery ritual and military respect, honoring Yang—though an enemy—as "a true warrior.

[citation needed] After the end of the Second World War, Yang's severed head was recovered by the Communist forces, rejoined to his body, and reburied with full military honor.