I have very minimal knowledge on this subject. All I knew is there are four yuga and they keep repeating. Yuga in my understanding is the age (or the period of time) of the world (not limited to earth)
Our Epics seem to have occurred during the end and start of old and new yuga respectively. The change over seem to have preceded by a devastating war.
How devastating was the Raamaayana or Mahabharata war. Were they worse than the World War 1 and 2 (including ongoing war on terrorism and property expansion war)