City States are much too trusting

[NordicExpanse]

I'm playing a war-monger game (yes, counter-productive, but so much fun!) and so far, I have taken three city-states using a rather simple strategy. I surround the city with troops, put my range attack pieces one or two tiles out and bam!, it's mine in two turns. Regular civs at least come out and say "Hey, what's with the troop build-up?" and unless you have an open border agreement, you can't very well surround their cities with troops.
City-states (and I suppose civs as well) should have the option of launching a pre-emptive strike in such an event. Plus, with the war-monger penalty being what it is, drawing the other team off-sides, so to speak, could even the playing field in the points arena.

 

[Silverman6083]

What's even worse is peacing out every turn after using your artillery, so that they don't even get a chance to survive!

 

[Fabio1701]

I agree, if you have the time to prepare and are not behind in tech it is quite easy. If you are behind in tech, not so easy. But them pre-emptively attacking you will only delay the inevitable: your decision to take it over. You can still mass your armies just a bit farther away: your decision to invade should be strategic point that a CS can influence. At the moment, your decision relies on warmonger penalty and possible alliances. Other risks should include CS having nuclear weapons and oterh game changers as I described here:
http://forums.civfanatics.com/showthread.php?t=520833