Yours seems a rather benign view of chemical weapons. Agreed, conventional weapons can be indiscriminate but need not always be so.  Precision strikes and restraint are possible (such as the most recent attack on Syrian targets appears to have been). Chemical weapons by their very nature are always indiscriminate. They may dissipate but in the process of doing so only increase casualties.  This inability to be 'targeted' is one reason they were banned in the first place. As far as being used for propaganda purposes this latest chemical assault assault on Syrian civilians is not an isolated incident. As I said, there have been 9 such attacks this year alone.  There has been long standing agreement that their use was beyond the pale - something the Syrians conceded when they agreed to "destroy" their arsenal. Land mines have been a long standing scourge and were addressed via the Ottawa Treaty (1997). AFAIK, we no longer see the sowing of these weapons as in Cambodia and other theatres.