When is a good time to go to war?

[m. of procrast.]

Of course, I see that when it comes to Civ5, I am a bit of an imperialist. I just need to conquer lands. But there has been something that has been puzzling me:
-I have the second largest military in my single player game
-I have a looming threat above my borders: The Greek Empire.
-But, they are the ally of a nation I am trying to repair relations with
-I have reasonably large settlements near the border
-This ally I am trying at repairing relations with has the bomb in a city above one of my major cities
-We are historic enemies, who were at war once before, as I repelled a small invasion they had against me.

What should I do?

 

[oPunchDrunko]

Got any screenshots?

 

[Vintage Port]

Pay someone gold to go to war with your long time enemy who has "the bomb".

If that won't work, pay the enemy with "the bomb" to go to war with someone else. Keep them busy.

Then you can decide who you want to attack. If you are worried about a Civ or 2 you either need to bite the bullet and go to war with them and push them back/cripple them and/or pay someone else to war with them.

The other option is to pay your enemy to war with someone else and while their troops are busy you can hopefully sneak in the backdoor and cripple them.

If you have the 2nd largest army it is good to put it to use. You are likely paying a good amount of upkeep on the units so might as well start conquering some cities to puppet and get some gold.

 

[Sabrina]

If your enemy already has the bomb, I'd say you waited too long. In this case, I'd do what the poster above said "keep them busy".

 

[pilot00]

Start WW3 by bribing them all and stay neutral. Once the nuclear exchange happens you can steam roll them all and be done with it. Or simply remove the one who treatens you the most.

It worked in my last game, though if it was reality, indeed the ship to Alpha Centauri would be our last hope...Half the planet was reduced to a radioactive wasteland with my citizens lamenting the destruction of the far away lands.