Question about battles...

[H Gilmer3]

I'm new to this game and I've played the Serbian scenario three times. The best I've done is a draw and I started letting the game play out my battles.

Minor battle - Let's say you have 4 units. So, you pull 3 up to the next box, and then 1? to the front line box. Then you pull you last unit into the second line.

So it looks like this (somewhat) - X means no unit O means a unit. The first line has two slots for support and I don't think I get any support units as Serbia.

First line X O X
Second line X X X
Third line none because you only had 4 units.

Do you always push the highest number to the first line like a 5-6-5? After the first skirmish, sometimes you switch them out?

Seems like the Serbian battle I always seem to be overwhelmed by the Austrians after my 5-6-5 units gets worn down. Then it's a 3-4-3 up against another of their 5-6-5s or so.

[Halus]

Yes, on the top line, the first space is for support (shock troops, afv or aircraft but only if you have succeeded in support arms research). The middle slot is for an infantry unit and third is artillery. You should put the rest in the 2nd line - unless you are defending a two pronged attack. After each round you should switch and bring a fresh unit into the top line, otherwise keeping the same unit there will tire it and it won't be available for the rest of the battle or will take excessive casualties.
I think it's good policy to start off with your strongest unit. Only time I start with a lower level is if I know the attacker is weak and I want to make sure there will be at least a 2nd round fought so I can select a breakthrough/counter-attack.