|Leads To|| ·Extra Barricades (with Concrete Barricades)|
|Effect||+$7500 to treasury|
"Send for reinforcements! We urgently need a $7500 loan!"
This research by itself is not too useful ; while $7500 is a lot, it's less help than what superior towers or barricade can do. However, it's a prerequesite for Special Supplies, who can be awesome for the last level, and the somewhat situationnal but sometime useful Extra Barricades and Extra Mines.