That's Simple. To get ahead of the Enemy. War is all about getting ahead of your enemy in anyway possible, sometimes by numbers somtimes by development of new arms. Take ,for example, near the end of WWII, Hitler's Germany developed the First Jet fighter, it was nearly unparelled, fortunetly for the world, it came too late. The Lufwaffa (germany's Air Force) was nearly out of money and out of skilled pilots. If the Jet came say, in 1943, We might not have won. Glad to Help
Because the old weapons become to common and considered to be to predictable
Some are
germ warfare
Same reason they always invent new weapons - to help them win. Superior weapons go a long way to help win a war. America has ruled the world because of superior fire power.
GrenadesFlamethrowersTanksMachine gunsPoison gas
Because they needed new weapons to improve their fighting against the opposing country.
To fight a war weapons, tanks, aircraft, ships are needed. This created jobs that were the by product of the war.
Chemical weapons and the machine gun
M16
The new weapons of world war one were machine guns,Tanks,poison gas, and planes og WW1
Tanks
Because the old weapons become to common and considered to be to predictable
Germany did
Some are
germ warfare
in world war 1 Germany introduced the use of chemical weapons for instance the Mustard Gas artillery shells, theses weapons where mainly used by countries on there side.
Same reason they always invent new weapons - to help them win. Superior weapons go a long way to help win a war. America has ruled the world because of superior fire power.