Vietnam veteran is a phrase used to describe someone who served in the armed forces of participating countries during the Vietnam War.

The term has been used to describe veterans who were in the armed forces of South Vietnam, the United States armed forces, and countries allied to them, whether or not they were actually stationed in Vietnam during their service. However, the more common usage distinguishes between those who served "in country" and those who did not actually serve in Vietnam by referring to the "in country" veterans as "Vietnam veterans" and the others as "Vietnam era veterans". The U.S. government officially refers to all as "Vietnam era veterans".

In the English-speaking world, the term "Vietnam veteran" is not usually used in relation to members of the communist People's Army of Vietnam or the National Liberation Front.

Although exact numbers are difficult to ascertain, it is safe to say that several million people served in the South Vietnamese armed forces, the vast majority of them in the Army of the Republic of Vietnam (ARVN)—between 1956 and 1975. It is known that during 1969–1971, there were about 22,000 ARVN combat deaths per year and the army reached a peak strength of about one million soldiers during 1972. The official number of anti-communist Vietnamese personnel killed in action was 220,357.

Vietnam ( listen), formally the Socialist Republic of Vietnam (Cộng hòa xã hội chủ nghĩa Việt Nam;  listen), is the easternmost country on the Indochina Peninsula in Southeast Asia. With an estimated 91.5 million inhabitants as of 2012, it is the world's 13th-most-populous country, and the eighth-most-populous Asian country. The name Vietnam translates as "South Viet", and was officially adopted in 1945. The country is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea to the east.

The Vietnamese became independent from Imperial China in 938 AD, following the Battle of Bạch Đằng River. Successive Vietnamese royal dynasties flourished as the nation expanded geographically and politically into Southeast Asia, until the Indochina Peninsula was colonized by the French in the mid-19th century. The First Indochina War eventually led to the expulsion of the French in 1954, leaving Vietnam divided politically into two states, North and South Vietnam. Conflict between the two sides intensified, with heavy foreign intervention, during the Vietnam War, which ended with a North Vietnamese victory in 1975.

A police officer (also known as a policeman or policewoman, and constable in some forces, particularly in the United Kingdom and other Commonwealth nations) is a warranted employee of a police force. In the United States, "officer" is the formal name of the lowest police rank; in many other countries "officer" is a generic term not specifying a particular rank, and the lowest rank is often "constable". Police officers are generally charged with the apprehension of criminals and the prevention and detection of crime, and the maintenance of public order. Police officers may be sworn to an oath, and have the power to arrest people and detain them for a limited time, along with other duties and powers.

Some police officers may also be trained in special duties, such as counter-terrorism, surveillance, child protection, VIP protection, and investigation techniques into major crime, including fraud, rape, murder and drug trafficking.

Responsibilities of a police officer are varied, and may differ greatly from within one political context to another. Typical duties relate to keeping the peace, law enforcement, protection of people and property, and the investigation of crimes. Officers are expected to respond to a variety of situations that may arise while they are on duty. Rules and guidelines dictate how an officer should behave within the community, and in many contexts restrictions are placed on what the uniformed officer wears. In some countries, rules and procedures dictate that a police officer is obliged to intervene in a criminal incident, even if they are off-duty. Police officers in nearly all countries retain their lawful powers, while off duty.