Brush Wars Star Trek Original Series

The Brush Wars were a series of conflicts that took place in the mid-20th century on Earth, in the continent of Asia. They were characterized by two superpowers aiding and assisting lesser nations in their conflict with each other. The Brush Wars went on "bloody year after bloody year," according to one 23rd century observer.

The Brush Wars were unpopular in some countries on Earth, with riots breaking out, in particular among young student popuations. One such riot was held at Santa Cruz in 1967, requiring police forces to break up the riot with tear gas. 

In 2268, Captain James T. Kirk compared the Brush Wars with the conflict on the planet Neural, stating that the situation of supplying rifles to both sides in a civil war, countering interference by the Klingon Empire, was very similar to the situation which had developed on 20th century Earth. Kirk further stated that the results of giving one side enormously superior weapons would result in destruction on a planetary scale. 

Background
According to interviews with Original Series cast members, aired during the opening of the Star Trek Smithsonian Exhibit, the Brush Wars were intended to be directly analogous to the Vietnam War.

A speech given by Lokai in also ties directly to the Vietnam War, with Lokai asking the Enterprise crew their thoughts on "being sent to fight a war on another planet in a battle that will serve your oppressors and bring death to you and your brothers."