In what ways was World War 1 a turning point in global history?

Answer 1

This question has many answers I summarize SOME of them.

The war started the disasemmbly of the European Colonial Empires, wrecked the econimies of several nations, jump started the Econimies of others, revolitionized warfare (this was the first war where tanks were used and also aircraft in a combat role)

Several nations started the road to freedom here, Canada established itself as a formidable fighting force at the battle of Vimy ridge.

Of signifigant importance to the modern world was the dissolution of the Ottoman empire. That empire had ruled from Egypt to Turkey and several Balkan states. It's dissolution into the many middle eastern states of today set the stage for the chaos of the modern Middle East.

Answer 2

Apart from the brouhaha in the Balkans, it was because of the pacts between various countries agreeing to get involved if they were attacked.