When Did The Vietnam War Begin?

Wow!  That's a very difficult question to answer.  Ho Chi Min actually went to France at the end of The Great War (World War One) to talk to U.S. President Woodrow Wilson about Vietnam being recognized as an independent nation.  Recall that Wilson's idea to help prevent future wars in Europe was the League of Nations (which failed, but gave rise to the United Nations at the end of World War Two).

Vietnam was a French colony.  There were certain people within Vietnam who wanted this to end, Ho Chi Min being one of them.  Ho Chi Min couldn't get help from Western countries, however.  Instead, he turned to the enemy of Western culture, Communism.

Unofficially documented, but easily found in the accounts of Vietnam War Veterans is that China was advising Vietnam in how to fight the forces of the United Nations.  Of course, the U.S.S.R. Was helping equip the Vietnamese forces.  The United Nations had to make a choice: Allow Communism to spread, or to make a stand.  (These were heady days of the Cold War, which are forgotten by younger generations today.)

You see, Ho Chi Min didn't simply want to free his country of French occupation, but he wanted direct and absolute control.  Tyranny was his objective.  In the end, with rules so tight as to make victory impossible, the United Nations pulled out of Vietnam, leaving the people of the South victims to Ho Chi Min's control.

So, to answer your question directly, the outbreak of war began in 1954.