Arsenal

The Arsenal is the third level of the War Factory: everything the Advanced War Factory builds, plus the Tempest, the Salamander, the Bulwark and, with Ballistic Missiles research, the Scorpion. Upgrading to it needs a Radar Station standing, and the line builds nothing for the 45 seconds the upgrade takes.

How to use

That downtime is the price. At the Tier-3 stage 45 seconds is a wave, so take the line offline when the front is quiet, or keep a second factory at Level 2 to cover it. The Tempest is the reason to pay it: the rocket artillery that ends a siege is built here. The Salamander and Bulwark are specialists (a siege mortar that burns its own escort, an escort that cannot shoot), so add those when you have seen what they answer: turret clusters behind Missile Interrupters, and rocket artillery. Losing the radar blocks the Tempest, Salamander, Bulwark and Scorpion, as well as the inherited Mammoth and Owl, until a radar stands again. Units without that requirement remain available.

With your completed Headquarters Lv.2 standing, Engineers can also build this line directly at Lv.3 for 1,640 metal, taking 90 seconds. The Radar Station and a free production slot are still required. A line already founded keeps building if that HQ is lost.