The phrase "robot army" refers to a group of robots working together. It implies that they have been programmed to perform tasks as a collective unit, often with the potential to outnumber or overpower humans. Full definition
That flying robot army shows why it makes sense to craft a movie around an evil genius from another planet: It gives the writers license to dream up pretty much anything they want. (slate.com)
All this takes place in a unique desert world, populated by a rogue robot army. (windowscentral.com)
The story behind this DLC is that there is a new enemy called The Mechanist, who has released an evil robot army on the wasteland, and your mission is to find out why, with the help of... (playstationing.com)