I've got Gas...

[Lucid]

The inclusion of chemical weapons is one of my favorite things about the modern campaigns game series. I tend to play as the Pact a fair amount (everyone else seems to prefer NATO for some reason), and so I've been motivated to think a fair amount about the wisest way to use the chemicals.

The conclusion I've come to is that, in the games like in the real world, chemical weapons are primarily defensive weapons, and only really useful for area-denial.

The means that the Pact player should resist the temptation to use chemicals until his advance has ground to a halt, and then should use them defensively to make it hard for NATO to push him back. Between his artillery mines (I rarely use more than 4 or 5 of those during my advance as the Pact) and his chemicals, the Pact player is well-equipped to throw down a nearly-impregnable defensive line when he thinks he has reached as far west as he can go.

Chemical weapons are (in game terms) basically "super-minefields". If NATO were free to use chemical weapons from the start, they would have a much easier time stopping the Pact advance, by blocking critical road junctions and bottle-necks, or worse, sliming bridge-heads over the Weser. Nothing sucks worse than when you finally build a bridge over a contested river, and your opponent puts chemicals on the far side of your new bridge.

A Pact player with guts realizes that there are times when he must drive a whole line of units in T-mode through a minefield and that the losses are less significant than the movement penalty from the mines....but the costs of driving through a chemical hex are so prohibitive that it basically never makes sense to just grit your teeth and drive on.

Another factor for chemical weapons favoring the defender:
Massing many units in a single hex is a tactic that favors the aggressor (by increasing their ability to concentrate force in order to breakthrough a narrow section of the enemy line), and chemical weapons are good at punishing that technique. It is SUPER satisfying to throw chemicals into a hex containing four or five good NATO tank units, and this is basically guaranteed to blunt the spear of the NATO attack.

If things go well for me in a campaign as the Pact, and I think I can drive off the west edge of the map, I will never use my chemicals. Chemicals should be the Pact's insurance against getting pushed back from their line of furthest advance.