The showed americans the vietnam war was not nearly over, as the government had suggested.

The correct answer is:  

Tet Offensive.  

The Tet Offensive (1968) by North Vietnam and the Viet Cong, was one of the most extensive military operations of the Vietnam War. It started on January 30, via units of the Viet Cong and North Vietnamese People's Army of Vietnam attacking the South Vietnamese Army of the Republic of Vietnam, the United States Armed Forces, and their allies.  

with my recent question

it broke up the ottoman empire (just a small fact) and the turkish leaders lost many soldiers.