Chemical horror

Today UK MPs rejected military action against the Syrian government despite the recent nerve agent attack killing hundreds of civilians. While I think that this was the right decision in the current circumstances, I've heard a lot of objections to military action along the lines of "civilians get killed in larger numbers by bombs, gunfire, napalm and starvation - what's so different about chemical weapons?" Playing Devil's Advocate, here's my answer.

Chemical warfare generally involves saturating a target area with a chemical agent for one of two reasons:

1. area denial; making it impossible or at least unattractive for opposing forces to occupy a strategically or tactically advantageous position; or
2. short-term offense; aiming to kill or debilitate concentrated opposing forces in an attractive location.

Modern chemical weapons such as the nerve agent sarin (one of the possible culprits in the recent attack, and one of the weapons likely used at Halabja) are devastatingly effective against any unprotected people in the immediate area; even gas masks aren't effective, since nerve agents can be absorbed through the skin. Full personal protective equipment is required to protect against a nerve agent attack. Modern armies can afford this for their troops - although the equipment makes them less effective and more susceptible to heat-induced illness - but there's no practical way to protect adequately a civilian population. Nerve agent attacks are therefore very much a 1-shot weapon from a military standpoint, advantageous if they can take opposing military forces by surprise, but with very little sustained effect if the forces are warned and well-equipped.

If an attacker has free use of chemical weapons, and little fear of reprisal, their best tactic is therefore to saturate target areas with nerve agents. As well as nailing any poorly-prepared opposition soldiers, this will force the properly-equipped military to button up in protective gear and be less efficient in communication, manoeuvre and combat. It's not a decisive win, but certainly an advantageous tactic. The side effect of this saturation, however, will be devastating to any civilian position both in the location and downwind. Lacking effective protective gear, casualties in any populated area will be horrendous - and completely irrelevant in military terms.

The international opprobrium in use of chemical weapons is therefore (unusually) for a good reason. It aims to make chemical weapon use, which is normally not a terribly efficient military method but disproportionately devastating in civilian casualties, a much higher cost for offensive forces than conventional weapons. The cost of conventional artillery and airstrikes is roughly proportional to the number of weapons used, and hence incentivises the attacker to target military forces as accurately as possible. Chemical weapons have no such incentive, and so there is a natural incentive to saturate the target area (maximising deterioration of effectiveness of the opposition) which has the side effect of civilian annihilation.

Back to the original question: why is killing a civilian with chemical weapons worse than killing them with a bullet? It's because unfettered chemical weapons use will devastate a civilian population in short order. We have forgotten this because the threat of nuclear retaliation has kept chemical weapon usage to relatively low volumes in the past 95 years. If we want to see many more thousands of chemical weapons deaths, we should treat chemical weapon usage like artillery usage.