Who was French commander in the Vietnam War?
Christian Marie Ferdinand de la Castries commanded at Dien Binh Phu.
One of the main reasons was to separate the Vietnam War from the French War or French Vietnam War (which is often referred to as the French Indochina War; and lately, the 1st Indochina War). To makes things simple: The French Indochina War and the US (American) Vietnam War, might be the easiest way to remember it.
Unfortunately, before the Vietnam War, as you know it, Vietnam was still embroiled in war. Another words, before the Vietnam War, there already was another war in Vietnam...the 1st Indochina War (also called the French War). And before the French War was the Japanese occupation during WWII...which was a guerrilla war fought against Imperial Japanese occupation forces (supported by the US/Allies).