A convoy is a group of vehicles (of any type, but usually motor vehicles or ships) traveling together for mutual support and protection. Often, a convoy is organized with armed defensive support, though it may also be used in a non-military sense, for example when driving through remote areas.
While the convoy was traveling through the desert Magneto tried to escape but despite his best efforts he could not. Suddenly the truck he was held in swerved knocking Colonel Chaffy and a scientist off their feet.
Apparently the convoy was sinking into the ground. The White Queen was using her telepathy to make the soldiers think they were sinking in quick sand and they all abandoned their vehicles. She then made a psychic spear and disrupted the power in the truck, releasing Magneto. Magneto then took Chaffy's gun and broke it apart.
He then threw Chaffy into a canal. When a soldier asked if he was alright Chaffy lamented that with Magneto loose no one was safe.