This only works on the first mission of the Soviet Campaign. After destroying the grand cannon 3 Amph. Trans will be sent to you but be quick to command one of them before they leave the map. Take it on the time machine until you go back to the time of the Dinosaur. After the time travel, quickly send the amph. trans to the norhtwestern part of the map. You'll then discover a trap T-rex. You can commnd T-rex but don't put it inside the amph. trans. You can then use it after you go to the future!