Chimeran Gun Tower

Gun Towers
This is a form of Chimeran technology that plays a role in the first mission of Resistance Retribution. Maquis intel said that Rotterdam was clear, but when two weeks later Operation Overstrike began the coastline of Rotterdam had already been fortied by the Chimera, indicating just how fast they can work. When the first squadron of British troops attempts to fly over Rotterdam, many of their VTOL aircrafts are shot down and the survivors are scattered all across Rotterdam. Steven Cartwright, first squadron's commanding officer, wishes to take down these gun towers to make sure that Rachel Parker's second squadron does not get the same welcome the first squadron recieved. Along with Roland Mallery, Raine Bouchard and James Grayson he succeeds in destroying the gun towers. At the end of the mission, Rachel Parker mentions the following:

If the Chimera were able to do this in two weeks, then what would we find in France and Germany, which the Chimera had been occupying for two years?

Different
In the Intel documents that are scattered across the level, Grayson mentions how these gun towers are different from any Chimeran tech he has ever seen, and believes that the Chimera are capable of so much more than they have shown. Another possibility is that these Gun Towers aren't even Chimeran, and that another alien race developed the technology used in them.