Answer:
The cause of World War One was the creation of complex alliances and the assassination of Archduke Franz Ferdinand. These two things combined caused the war to more devastating than war in the past.
The reason that world war one was so much deadlier than past wars is the weapons that were used. Planes, submarines, machine gun, gasses, and tanks were being used in combat for the first time. These innovations made world war one far deadlier than any other war since then.
Step-by-step explanation: