system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5- Tactically, where did the US go wrong in the Vietnam war?
gpt
You're not using the word "tactically" properly.  Tactics is the hour by hour planning of a single fight.  Wars are only lost tactically if there is a huge pitched battle that crushes an army or navy, like the Battle of Midway or Waterloo.

*Strategy* is the overall planning of a war, from supplies, weapons used, units brought into the theater, tactics they employ, and final objective.  

The US did not have a strategy for victory in Vietnam.  In conventional war, capturing the enemy capital city is often the objective; the US never invaded North Vietnam at all, as this would have caused China and the USSR to become involved.  Instead, they tried to fight communists in South Vietnam and hope they would get tired of fighting and quit.  In fact, after the Tet offensive, the North Vietnamese were just about ready to stop active military campaigns in the south, but the threat wouldn't have ended at all.