How do you ally a faction already at war ?

[Shahed]

The story.
1. Hungary attacks Turks (yours truly--> me)

2. I completely wipe the toilet with them taking every province they own, and utterly decimating every army they have. I lose maximum 100 men in the whole campaign, they lose 3000 or more. I release all prisoners and occupy cities without sacking or murder (somehow the Sultan gets "The Tyrant" title though ???)

3. I don't want all this land but I figure I'll take it and use it as a negotiating chip. They refuse and refuse and refuse, apprently they got pissed by getting such a beating. So they won't take the land back (LOL).

4. Backstabbing Venetians (allies) attack Constantinople.

5. Leaving minimum militia in Hungary, I proceed to wipe the floor with the Venetian Army. The Venetian Navy sits comfortably at the bottom of the Adriatic, never to be heard of again.

6. Venetians make peace. Great ! I give everything back to them PLUS 30K Florins to repair their sorry behinds. Now they have a lot of converts to Islam since I sent 5 Imams per province. So they lose Thessaloniki due to religious unrest to Muslim rebels (LOL). I go and take it back, and give it back to them (with a Jihad no less). They had no army left so they were never going to take it back for years.

7. Been about 8 years since I spoke to the Hungarians so I go back and ask for peace in return for all their land PLUS 25K Florins. They reject. I ask for vassalage and all their lands back PLUS 35K Florins, PLUS 5K Florins per turn. They reject.

8. I go to the Poles and gift them all of Hungary PLUS 35K Florins.

9. Case closed.... or is it ?

10. Hungarian diplomat shows up at Constantinople. BORAT gets his knife out, gets on a ship from Alexandria to come kill the diplomat, BUT the diplomat offers peace. Fine, accepted, but here have 20K Florins for the road too as a gift.

11. Hungarians attack Poland, Denmark attacks Poland, Russia attacks Poland. Milan Attacks Venice and HRE. France already in a war with HRE, get attaked by Spain and England.... !!! So the whole of Christendom goes to war with itself. Ohh I forgot Sicily and Venice were already at war, so they carry on with that.

The plan.
Now my objective is to FINALLY get nasty with the Egys for Jerusalem. I want to hold Constantinople as a choke point and fight battles against anyone who wants to right outside the gates. I want to go all the way to Morocco and eliminate the Muslim factions, first.

The problem.
The problem is that Poland is now getting creamed and Denmark will soon be at the Black Sea. I see this as a threat to my trading income because a powerful single nation will surely attack me.

I want to join the Poles into an Alliance and send expeditionary forces (2 Cavalry armies and 1 defensive infantry army) to hit the Danes in particular but also the Russians. I want a strong neighbour (but not the most powerful in Europe) to the West with whom I conduct the majority of my trade from Constantinople.

The Question.
Whenever I do a diplomatic mission though, I don't get the option to ally. How can I do this ?

[FactionHeir]

You can only ally with a faction if:
1. It is not allied with a faction at war with you
2. It is not on a crusade against you (and possibly must never have?)
3. You are neutral with them
4. Not allied to a faction that was at war with you and is now eliminated (a bug)

[Shahed]

Come to think of it. When I made peace with Venice it gave me a message saying hosilities cease Turks-Byzantium.

Venice is actually at war with almost everyone and their rating is Very Untrustworthy. But I am no longer allied with them. I am allied with the Danes, that's the problem... That was an easy alliance in the beginning, guess I am stuck with it.