Use of CS in war is prohibited under the terms of the Chemical Weapons Convention, signed by most nations in 1993 with all but five other nations signing between 1994 and 1997. The reasoning behind the prohibition is pragmatic: use of CS by one combatant could easily trigger retaliation with much more toxic chemical weapons such as nerve agents. Only four nations have not signed the Chemical Weapons Convention and are therefore unhindered by restrictions on the use of CS gas: Angola, Egypt, North Korea and Somalia.