This command toggles (enables and disables) the delay that usually is present between declarations of war - i.e. after using this command, wars will start instantly after declaration (typing it again returns behaviour to usual).
The syntax for the instant_war command is as follows:
Find below working examples of the instant_war command.
As instant_war is a toggle command, running the above command with instant war disabled (default) would enable instant war, making war start instantly after a declaration is made. Running instant_war again after having enabled it will toggle it off (disable it).