Complex sentence: After she unsuccessfully ambushes him, he explains that he saved her life by finding her wreck and bringing her here, because there has been a massive attack-possibly by Russians or Martians-and everyone else is dead.
Split into simpler sentences: After she unsuccessfully ambushes him, he explains that he saved her life by finding her wreck and bringing her here. There has been a massive attack-possibly by Russians or Martians-and everyone else is dead.