Shortly after the end of World War I, a strange radio communication known as the "Broadcast" causes deaths across the world, sparing two war veterans - Frank Woodruff and Vladimir Farnsworth. While Woodruff builds 'mobile trenches' to help disabled soldiers, Vladimir builds 'monovisions'. But becoming bent on world conquest, he uses his monovisions to lay monovision cables across the world. It is now up to a Woodruff's mobile trenches to lead the counter-attack and save the day.

Iron Brigade is a unique hybrid of tower defence and third-person shooting in which players fight off the evil monovisions, using their fully upgradeable mobile trenches, and deploying turrets to help stem the tide.