Or in other words how to dominate...
The game is pretty flexible so you can achieve your goals in a variety of ways.
If you have ample time on your hands, you can outmaneuver most foes and make sure there isn't much they can do to you when you go offline. The more you keep an eye on things the less force you would actually need to maintain order.
For those of you who have many other things to do than play a lot, you can plan a development strategy and manage things enough to keep the train rolling. The secret stash provides enough of a buffer zone to make sure you have ample supplies left even if you are quite passive. Being plundered occasionally isn't going to be a problem if your construction and research is going normally.
If you really like the fighter role, you can go aggressive and show every weakling who is boss. Keep in mind however that maintaining a large army has its costs and can syphon a lot of funds you can otherwise use for development.
Knowing when to strike is half the battle. Simply having the largest and strongest army isn't a guarantee for victory. If your espionage is inferior you may end up hitting a city which is almost empty. The enemy can learn soon enough about your attack, and send a counter strike – full of faster troops that can hit you sooner than any of your armies can get home. Enemies who have focused much more on military may have much slower and more expensive research, construction and armaments.
Battles do not completely destroy either side. So making one mistake isn't going to cost you everything. This makes sure you have enough left over to keep the weaker players at bay and interact with NPCs normally.
We've seen this problem before with other games. Someone hits you and your entire army is dead. Now what? Spend 1 month to get a new one? Quit the game? You can’t even loot the miserable NPC next to you.
Grand battles are cool, but investing weeks and weeks into just one fight is silly and we have done much better than that.
So, keep your construction and expansion flowing well, research to keep up with advancements. When you open the armory, you can leap much forward in strength - each step in there gives a worthwhile advantage for your units.
Just wait and see when Siege, Alliances, Heroes and Items get introduced. It will be a glorious fight with thousands of contenders.