A budget title that lives up to its asking price.
Operation Vietnam is pretty much a modern-day version of Cannon Fodder. There are a couple of similar games out there (Elite Forces: Unit 77, The B Team), but the pickings are still pretty slim on DS. If you're into simple tactical shooters, you'll likely dig this game. It was released at a budget price, and you can likely find it dirt cheap these days.
You control four dudes -- an all-around commando, a sniper, a medic, and a heavy artillery guy -- switching out on the fly to navigate through worn-torn Vietnam. The game's more Rambo than it is tongue-in-cheek, but it's still a fun little romp.
The controls are pretty straightforward, with the D-pad handling movement of your leader character and the face buttons mapped to shooting, tossing grenades, etc. I think I would have preferred an approach similar to Geometry Wars (using the stylus to aim), but an auto-lock-on mechanic keeps things manageable.
The gameplay consists of little more than slinking your way through environments, aggroing enemies in bite-size numbers, and collecting dog tags and opening gates. Still, the design is solid, and the missions are portioned out nicely.
The graphics are enjoyable. The view is top-down, and the character models are teeny, but the 3D environments look good. It's a satisfying presentation, and there are some decent sound effects to boot.
Personally, I think Elite Forces: Unit 77 is more interesting when it comes to this type of tactical shooter on DS, and The B Team is a whole lot funnier, but Operation Vietnam is another worthwhile addition to the genre on DS. It's nothing to go crazy over, but folks who go in for this sort of thing will likely appreciate it.