The Grumble is a Soviet stolen tech unit acquired by infiltrating an AlliedTech Center and Construction Yard. Arguably one of the most powerful anti-air weapons in the war, it can easily bring down enemy aircraft in its way.
However, one has to take note that the Grumble must be deployed first before it can fire and it cannot attack aircraft that flies too close.
The Grumble is the Soviet response to the continuously expanding Allied air force, available once Allied technology has been carefully researched by Soviet spies. With a set of massive rocket launchers, the Grumble is capable of eliminating any type of aircraft at great ranges when deployed.
The Grumble has no means of defending itself against ground targets so it requires support from other units. It also has a minimum range that enemy aircraft can approach and stay safe in so remember to create your Grumble defense line wisely and don't leave any "dead zones".