Katyusha was the name of the WWII Russian Rocket launcher. Thee were fired from the back of the Truck, one rocket fired after another (This was one for if you fired ALL the rockers at once, the truck the launcher was on would be tipped over AS the rockets were launched).
The question is was this launched from a traditional launch vehicles (i.e. a truck) and launched all at once (i.e. pulled up, Cover over the Rockets lifted and the rockets fired at the target, possible but highly unlikely). OR did the insurgents do what the Viet Cong did in Vietnam. Take these rockets, and fired them one at a time after carrying them to various launching sites in smaller vehicles or by foot? This sounds more likely, but that means the insurgents could coordinate FIVE groups to all fired about the same time. Either way it is NOT a goof sign for the American War Effort.
These are all standard size army trucks i.e. 2 1/2 or 5 ton jobs, nothing custom built, through the trucks had the Rockets launcher permanently attached to their cargo beds.
The BM-21 has 40 tubes of 122mm Rockets, launch one after another
http://www.fas.org/man/dod-101/sys/land/row/bm-21.htmThe larger BM-24 has 12 tubes with 240mm Rockets:
http://www.fas.org/man/dod-101/sys/land/row/bm-24.htmThe BM-25 has six 250 mm Rockets:
http://www.fas.org/man/dod-101/sys/land/row/bm-25.htm