What weapon changed the face of warfare?

most of the stuff we have mention did change the face of warfare u cant really put it down to just one thing
when you really look at it..its any weapon that extends the reach of the combatant..nessicating a change in the tactics in the defending party..

the knife

the club

the spear

the throwing stick with spear

the use of very long spears

the bow and arrow

the gun

the cannon

the missile

the guided missile

the ballistic missile

the inter continental ballistic missile

and beyond mans reach? whats next? :D
and if we do get further is it really a benifit or will it just keep on going till we eventually destroy our selves
Nukes changed it all that is correct.

But we still fight wars today and don't use nukes, so it doesn't affect us directly.

The machine gun is always in play and it's impact is felt in every war since it's inception.
The weapon that decided the fate of the USA surviving as a country was the repeating rifle and six shooter. "God created man, Col. Colt made them equal."
Mass media and the court of public opinion... that applied with the human nature of being sympathetic to the weak.
Which means when your troops are kicking some serious @$$, your population wants it to stop.
Depend on the century.

In 1500: century: Gun powder

1800: century rifle loaded behind, later bolt-action rifle

1900: machine gun, indirect fire, tanks, air force, nukes...

2000 century: media.
I would have to say the repeating rifle changed the face of warfare to a great extent. being able to fire faster or while moving. Also the technology led to the machine gun.
Combat aircrafts, both bombers and fighter planes, changed warfare.
The British Spitfire, American Mustang, and the German Messerschmitt are examples used in WW2.

German Messerschmitt

The British Spitfire

American Mustang
Maybe Fear.

If one side can't get fear into the other side's soldiers, often it can be put into the general populace.

It was also used in ancient times, promoted by displaying the size of an army, heralds, written messages or dead bodies hurled over barriers.

Terrorists use this tactic.

The greatest enemy we have to fear, is fear itself.

Must a weapon be a "thing." or can it be any action, thing or influence?