December 5, 1964

1964Vietnam War: For his heroism in battle earlier in the year, Captain Roger Donlon is awarded the first Medal of Honor of the war.^[†]

The Vietnam War was an armed conflict in Vietnam, Laos, and Cambodia fought between North Vietnam and South Vietnam and their allies. North Vietnam was supported by the Soviet Union and China, while South Vietnam was supported by the United States and other anti-communist nations. The conflict was the second of the Indochina wars and a proxy war of the Cold War between the Soviet Union and US. The Vietnam War was one of the postcolonial wars of national liberation, a theater in the Cold War, and a civil war, with civil warfare a defining feature from the outset. Direct US military involvement escalated from 1965 until its withdrawal in 1973. The fighting spilled into the Laotian and Cambodian Civil Wars, which ended with all three countries becoming communist in 1975.

1964Lloyd J. Old discovers the first linkage between the major histocompatibility complex (MHC) and disease—mouse leukemia—opening the way for the recognition of the importance of the MHC in the immune response.^[†]

Lloyd John Old was an American medical researcher, and one of the founders of the field of cancer immunology. When Old began his career in 1958, tumor immunology was in its infancy. Today, cancer immunotherapies are a significant advance in cancer therapy.