These sentences contradict each other. :blink:
It may appear to be contradicting, but trust me, they are both accurate.
The situation was a bit looney.
Jagiello intervened alot into Lithuanian affairs, for example, when his younger brother revolted in Vitebsk, he basically forced Vytaut to take care of him.
The alliance between Poland and Lithuania was not a sure thing either, as far as I remember Lithuania decided NOT to take part in war with Teutonic Order (now called thirteen years war).
They didn't. One of the reasons why Jagiello didn't continue on to siege Malbork after Grunwald and completely annexing the Teutonic Order and eliminating Prussia from the history books (which would've been totally awesome, screw the haters) is because Vytaut didn't really want to continue on with the war. (He had his own concerns at the time in Lithuania)
Mazovia is not a part of the Polish crown. And Poland doesn't have a claim on the land. So Mazowia is not a consideration, unless this has changed recently as well? So, its 20 vs. 27? I'll have to look at it.
You talking about in game?
Mazovia gave up it's independence and became a formal vassal of Poland sometime in the 1380's. Irregardless, Poland always had claim on the land.
The only reason they were independent for longer than other Polish polities and not conquered and incorporated into the Polish crown is because of the political maneuvering of Siemowit III after the death of his younger brother. (He allied with Pomerania, Bohemia and others, and then made a pact with Casimir that he would abandon his allies in exchange for peace) By the 1399 startdate of Eu3, Mazovia was a vassal of Poland because Siemowit's son, Siemowit IV, fought a rebellion against the Polish crown attempting to claim all of Poland for himself, but after the Union of Krewo, he realized his forces were too small in comparison to Poland+Lithuania, so he abandoned his claims and accepted formal vassalage. Siemowit III's other son, Janusz (who continued to rule Warszawa) also had some conflict with Vytaut while all this was going on but I don't recall what happened with him.
All in all, the reigns of Jagiello and Vytaut in Poland and Lithuania is in itself, amongst the most interesting portions of history in Europe in my opinion.
It's too complicated to get it right in game though because like I said earlier, it was looney. I much prefer the startdate of 1444.