As Swami Chinmayananda said, In the age of Krita or Satya, they lived apart in different realms, Devas in heavens, Daityas in nether world.
Next was Treta yuga in which both Rama and Ravana lived on same planet but apart in different locations.
Then came Dwapara in which both Pandavas and Kauravas beloned to same family.
Now we are in kali, in which both good and evil are present in the same person !
The battle has to be fought to subdue impulses that are lowly and despicable for triumph of good.
Also our scriptures tell us the presence of same supreme soul who animates the universe is also present with in. So when we win the battle within ourselves,after all it is rightly said the if one want to bring change in the world, change he too should become, it could be translated thus to effect the entire nation,nay entire cosmos if need be. That was how handful of people determined and dedicated could bring change, uproot established mighty empires of demonic forces in the past, imperialism, colonialism in the present and same way the evil of Islamist terrorism too will be vanquished.
G V Chelvapilla
Source: Chelvapila C. Via. Publisher@worldhindunews