Yes it was avoidable. But if there was peace keeping force or litrate people.
Explanation:
Peace keeping force is a group or mass of people who helps stop war all around the countries. So they could avoid world war 1 if there were peace keeping force.
No war is avoidable. The war itself can be fought later or sooner depending on what the reason for going to war is. The assassination of Ferdinand was an excuse to start the war, but the underlying reasons for fighting were far more serious than the assassination of 2 people (horrible as that was). The combatants were ready and willing to fight and all other avenues were closed to avoid a horrible confrontation.
