Complex sentence: Connor returns to the Resistance headquarters located aboard a nuclear submarine and is briefed by General Ashdown (Ironside) that the Resistance has discovered a hidden signal containing a code protocol which they believe can initiate a permanent shutdown of Skynet's machines.
Split into simpler sentences: Connor returns to the Resistance headquarters located aboard a nuclear submarine, and is briefed by General Ashdown (Ironside). The Resistance has discovered a hidden signal containing a code protocol which they believe can initiate a permanent shutdown of Skynet's machines.