What happened to the charge?

[DerBlitzer]

I've accomplished charges by laying down smoke the turn before---of course this telegraphs your intent, but since your opponent will likely see the force build-up, anyway, or anticipate an attack through a likely path, it probably won't come as a surprise. Hard to hide a charge. You need some units assaulting, some for cover fire, and always nice to have tanks or on-board howitzers to suppress with HE. Of course you'll lose units, so you need plenty.

You can also use to smoke in another area where you won't be attacking to make your opponent possibily shift some forces over there, weakening his defense for your actual charge.