Wait, do I need to buy CO if I already have Arma 2 and OA?

I'm confused.

Been a big OpFlash/ARMA fan forever. Bought ARMA 2 when it came out. Bought Operation Arrowhead when it came out.

Now, I'm surfing around this Day Z stuff and the new Czech DLC, and it says that Combined Operations is required.

Is Combined Operations different than just Arma 2 + Operation Arrowhead? Why can't I use DayZ and the Czech DLC with my original versions of Arma 2 and OA?

No you do not. "Combined Operations" is what you get when you combine (hence the name) Arma 2 and the expansion "Operation Arrowhead".

If you install the two games in the same directory and did everything correct, you have Arma 2:Combined Operations which enables you to use e.g. DayZ

No you do not. "Combined Operations" is what you get when you combine (hence the name) Arma 2 and the expansion "Operation Arrowhead".

If you install the two games in the same directory and did everything correct, you have Arma 2:Combined Operations which enables you to use e.g. DayZ

Yep, install ArmA2 first then OA, in the same place, and voilà, you've got ArmA2:Co.

Ok, thanks for clearing that up guys.

Another question. If I combine them into the same directory, can I use Arma 2 units in the OA maps and vice versa?

I think there was some talk about mods doing that, but I don't think the Arma 2 units have the correct IR heat stuff?

Another question. If I combine them into the same directory, can I use Arma 2 units in the OA maps and vice versa?

I think there was some talk about mods doing that, but I don't think the Arma 2 units have the correct IR heat stuff?

Some A2 units got an update since their base class was updated in OA. For example some HMMWVS and MTVR and M1A1,A2 and AH-64. here are simpler fallback IR textures for old A" units in OA.

USMC, CDF and Russian Army are still the natural choice when playing on Chernarus map. In 1.60 OA Patch even the T-90 got updated with a range finder and manual target range input.