How do you break an alliance?

If I remember correctly it's in the diplomatic window where you would ask for an allicance. Mid top right.

You should have break alliance as an optiion.

It's been a while so I might be wrong but I think it's there.

I still can't see it.  I tried to get a printscreen of the diplo screen so you could point it out, but it just came out plain black for some reason.  At the top you have the viewscreen plus you can use the pulldown menu to look at what trade, treaties etc they have, but it's non-interactive.  Then down the side you have all the things that you can give them or ask them for, but as far as I can see no actual option to negotiate or cancel any treaties.  Can anyone be a little more specific?

You have to be in the Speak To/Trade window.

Open Diplo, click the Drengin, and click Speak To. On the left, under Treaties, you should see Break Alliance.

It's not there, the only options are 'attack', 'surrender' and 'economic treaty'.

Could I have accidently started the gme in some weird 'team mode' that means we have a permanent unbreakable alliance?  As I said I'm fairly sure I didn't either propose or accept this alliance in the first place.

That's always a possibility.

I remember trying that option once creating a game with alliances already made. However I do not remember if I could break them or not.

Sorry

When I set up the game, I set everything as random, including how many opponents I would have and which ones.  The only things I didn't set as random were the tech speed (normal) and difficulty level (beginner).  Does randomising the number of opponents include some kind of random teaming?  If so is there any way to prevent that?

I'm pretty sure that choosing a random number of opponents does not cause Relations to be random. But it should have been a little hard to finger-check your way into a Team with the Drengin; you'd need to have clicked them on the Selected Opponents screen and then clicked the left arrow in the Relations spin box.

I wonder, does typing Kryo's name in a thread still magically summon him? He should certainly be able to help you figure this out.

Actually thinking back to my previous games (there have only been a few) in one of those I found myself in a team I didn't negotiate as well.  At the time I put it down to being a noob and probably accidently clicking on something I didn't mean to in the negotiations screen.  This has made me wonder though if there really is some kind of randomised teaming option.

You can look at the Relations screen, or whatever the screen is that has the colored lines between race synbols for treaties and war.

The "Team" line has a separate color.

When you have another civ selected in the Foreign Relations screen, you see the check box for Trade Embargo?  When you are allied to another race, that becomes the 'Break Alliance' checkbox.

Jim - Good call!  Confirmed we have the dark blue line so we are a team.  I guess this means that when you select random opponents it also puts you in random teams or at least has the chance of doing so.  Will need further investigation to confirm what the actual mechanic is.

Marvin - It has the Trade Embargo check box, which is a weird thing to be able to do to a team mate

You could try the #galciv IRC channel on the Community tab in Impulse (or irc.stardock.com in your favorite client).

There's often a dev or Kryo on there and one of them should be able to answer the question about whether teams are part of selecting Random opponents.

I must confess that I knew that only because I struggled with the same problem last year.  I finally had to stop the random opponent thing to make it stop. 

It is choosing random opponents that causes the problem or a random number of opponents?

In my case, I specified the number but had random selection toggled.

I was testing the effects on Colony Rush timing as the number of opponents changed with all else constant, but with varying races.