Ho Yinsen was a prisoner of the communist leader Wong-Chu in Vietnam. During this time, American inventor Anthony Stark was sent to Vietnam to supervise a field test of one of his new transistorized weapons. While in Vietnam, Stark tripped a booby trap. The resulting explosion lodged a piece of shrapnel in his chest. The gravely injured Stark was taken captive by Wong-Chu as well, and informed that the shrapnel would penetrate his heart within a week, killing him. Wong-Chu offered Stark at deal: if he would build a power weapon for the Communists, he would allow his surgeons to save Stark's life. Stark agreed, hoping to gain time and access to tools.
Stark was given access to a small laboratory in communist territory along with fellow captive, Professor Ho Yinsen. Yinsen helped Stark design and build an electrically powered suit of iron armor and equipped it with a variety of offensive weaponry. The armor also contained pacemaker-like device which would enable Stark's injured heart to keep beating after the shrapnel entered it. Donning the suit, Stark connected it to an electrical generator to charge. Lying on a table Stark was helpless until the suit was fully charged. His captor, Wong-Chu, sensed something was amiss and came to investigate with armed men. Realizing he was sacrificing his life, Professor Yinsen went out to confront Wong-Chu, giving Stark the extra time he needed to fully charge the armored suit. As Iron Man, Stark avenged Yinsen's death and scattered Wong Chu's guerilla troops.
It was found out later that Professor Yinsen had not immediately died from the gunshot wounds. He was teaching his knowledge to a fellow prisoner in the camp, a young man named Sun-Tao. After Wong-Chu ordered his men to fire on Professor Yinsen, he amusedly made Sun-Tao bury his body in the jungle. Sun-Tao was surprised to see that the professor still drew some breath. In his dying moment he passed on a notebook to the young man. Immediately afterwards, "The Great Salvager" appeared and wordlessly told Sun-Tao that he was collecting on an old transaction he had made.
Years later, Iron Man travelled to a mobile station named New Timbetpal inhabited by a group of monks led by Sun-Tao who believed that Professor Yinsen was their great teacher. Iron Man, along with a band of the monks swarmed a village inhabited by the evil tyrant, Wong-Chu, who had become one of the biggest drug lords on Earth. They were captured and told that Professor Yinsen was still alive. After the battle, they returned to New Timbetpal where Tony Stark was told he may see Professor Yinsen. It is then he found that "The Great Salvager" had only saved the part of him that he felt mattered: his living brain.