I finished it yesterday as well. I went after middle depot and just after computer made to it, I did as well. (thanks to transporter unit)
But while running after deport, that enemy artilery unit got strong. I did go after factory and at the end I had 3 units going after enemy's HQ.
And yes, it's code FIFTH for next level. Thanks again for sharing your strategy.
I didn't have a time to play this new level, but during this week I will.
LV (ID) Level Name
01 (16) CONRA
02 (17) PHASE
03 (18) EXOTY
04 (19) MOUNT
05 (20) FIGHT
06 (21) RUSTY
07 (22) FIFTH