Distant war cta penalty

[Phibs]

Is there a detailed description somewhere as to how exactly this mechanic works? (cta = call to arms)

Situation I found myself in:

Crimea, allied to senor Ottomanos & Nogai, who had Kazan as a vassal.
Nogai had taken a small bite out of the golden horde taking one province and giving another to Kazan.
I myself had vassalized Circassia.
Poland held a PU over Lithuania.

When checking my war options against Lithuania I noticed that Nogai would not join because of 'distant war', but Denmark +Sweden/Norway would honour their alliance with Poland.

I dodged the problem by declaring on the march ... Moldavia I think it is, but it got me wondering.

 

[VampireBoot]

Distant war doesn't apply to defenders.

 

[Phibs]

*Smacks forehead*

Of course, thanks!

And offensive cta? Is it province steps? Travel time? War target or all defenders?

 

[VampireBoot]

Not sure about this, but I believe it's based on the distance (not number of provinces; envoy travel time is based on the same thing) between closest borders among the two sides. In previous patches, I was able to e.g. call Poland into a war against Spain after Spain's ally Austria joins the war, so that implies the distance penalty is based on closest enemy.