After World War I a strange radio signal later just known as the Broadcast appears and kills many people. Two war veterans survive and gain somehow super-intelligence. But one of them, Vladimir Farnsworth, becomes mad and wants to spread the Broadcast around the world with his inventions like the robotic creatures called Monovision Tubes. The other survivor Frank Woodruff constructs walking weapons platforms called Mobile Trenches to help mankind in its battle against Farnsworth.
Iron Brigade is a hybrid of a 3rd-person mech action game and a strategic approach of tower defense. Before each mission you choose a specific Trench model. Its legs, weapons and towers called emplacements. Within the mission you are controlling your Trench, firing at the different Tube types attacking from multiple directions and trying to defend your position. With enough collected scrap from destroyed Tubes you can place towers almost without limitations which mostly attack the enemies, but also offer support with repairing or collecting scrap. You collect experience points and get new weapons and equipment for achieving different goals. Some things you can buy for in-game cash in a shop, but the best weapons are usually found on the battlefield. The whole game can be played co-op up to four players.
Due to trademark issues with the original Trenched name, the European release was delayed. When it was eventually released, it introduced a new survival game mode, new weapons and other extras. This was also patched into the North American version of the game.