G.I. Joe vs. the Transformers Comic Book, Vol. II #1

Synopsis

By using Cybertronian technology, Cobra builds a gate between Earth and Cybertron. During a skirmish with GI Joe, the gate is damaged, sending members of GI Joe and Cobra to Cybertron. Further feedback causes the gate to make several Transformers disappear. Ultra Magnus and Perceptor erect a forcefield to prevent Shockwave and his minions from accessing the gate or harming the humans. The Autobots reveal that the humans must travel back in time to retrieve the missing Transformers from Earth or further feedback will cause the reoccurring equivalent of a nuclear holocaust on Earth.