Name 3 way the ww1 had became a global war

Three ways WW1 went from being a localized European conflict to a global one: 

The declaration of war by Britain in 1914 brought the Commonwealth into the war involving far-away countries like Canada and Australia and India. 

One method used by the Germans to defeat Britain was sea blockade; by the German High Seas Fleet at the beginning of the war then with submarines later... this was counters by the British Home Fleet based at Scapa Flow. By trying to cut off goods being sent to Britain the war was fought at sea also in the Channel and in the Atlantic. 

Neutral countries like the USA joining later in the war in 1917 make WW1 an even bigger global conflict. 

A forth way is how the British, French and Germans all had colonies in Africa - and fought each other there also.