I have constant war all the time. My last game as the drones, the Hive (yes, I made a mixture of factions) surrendered to me when I, like, blitzkrieged his empire and he almost crushed the UN. I just saved them when they were on their last base and since I had planned, I crushed the Morgans. It was a fairly tough war since they had better tech, they mind control probed my captured bases from them, but I had far greater force. And the Hive warred with me for ages without any conflict with them. The planet was about 30-50% sea so they could have launched a ground attack which could have taken ages to get there. War always occurs, so when it happens, I'm ready.
My current game: I'm the morgans, The hive wanted me to attack the gaians, so I did. I didn't realize that they were on an island not far from me, so I attacked them whilst having Free Market and Wealth (and right now, I still have 'em!). The Hive wanted money and eventually it was from Pact to treaty, then a few years later, from treaty to war, and they had already crushed 2 factions. So I'm like fighting an empire and I've just captured almost all their sea bases, but they keep firing missiles at me!

But I'll show how powerful my defences are, thanks to certain projects.
Difficulty: librarian. Just need to clock all factions with that difficulty, then I'll go thinker.