Biological warfare (also known as germ warfare) is the use of biological toxins or infectious agents such as bacteria, viruses, and fungi with intent to kill or incapacitate humans, animals or plants as an act of war. Biological weapons (often termed "bio-weapons" or "bio-agents") are living organisms or replicating entities (viruses) that reproduce or replicate within their host victims. Entomological (insect) warfare is also considered a type of biological warfare.

Biological weapons may be employed in various ways to gain a strategic or tactical advantage over an adversary, either by threats or by actual deployments. Like some of the chemical weapons, biological weapons may also be useful as area denial weapons. These agents may be lethal or non-lethal, and may be targeted against a single individual, a group of people, or even an entire population. They may be developed, acquired, stockpiled or deployed by nation states or by non-national groups. In the latter case, or if a nation-state uses it clandestinely, it may also be considered bioterrorism.

The Korean War (Korean: 한국전쟁 or 조선전쟁, Hanja: 韓國戰爭 or 朝鮮戰爭; 25 June 1950 – 27 July 1953) was a war between the Republic of Korea (supported primarily by the United States of America, with contributions from allied nations under the aegis of the United Nations) and the Democratic People's Republic of Korea (supported by the People's Republic of China, with military and material aid from the Union of Soviet Socialist Republics). The Korean War was primarily the result of the political division of Korea by an agreement of the victorious Allies at the conclusion of the Pacific War at the end of World War II. The Korean Peninsula was ruled by the Empire of Japan from 1910 until the end of World War II. Following the surrender of the Empire of Japan in September 1945, American administrators divided the peninsula along the 38th parallel, with U.S. military forces occupying the southern half and Soviet military forces occupying the northern half.