Why was the world changing in the early 1900s? * Based from the text, what are the factors that changed the face of war?

If your talking about WW1 then the industrial revolution.

Explanation: There were many new inventions like.
Zeppelins- used to throw bombs without being noticed (especially during the night)
Airplanes- Was first used as a spying gadget, then later on used as throwing bombs (attacking enemies).
U-boats- (mostly used by Germany) Mainly for attacking boats underwater going unnoticed by enemies.
Tanks- Was used for safe transportation (supplies) or to attack.
Poison gas- (Mustard Gas!) was meant to distract and confused the enemy in the trenches to get them out of the trenches. Later found out that the gas was a great killing supply.
Machine guns- Better usage than normal guns. Has more room for amo and usually leads to stale mate.