OK. I'm Takeda. Allied with Hojo, I defeated Uesegi. Hojo turned against me, and I killed him in battle. His lands were inherited by Oda. Mori has steamrolled the left-hand side of the map, and has taken most Oda territory in the centre - I'm building up for a big confrontation when Mori reaches my borders. I ally with Oda so that when, inevitably, he and his heirs are killed, I will inherit his territory in the former Uesegi and Hojo lands.
On the very turn that Oda is trapped in a castle and killed in Owari, he decides to make an illogical, impossible attack on me, for the SOLE PURPOSE of breaking the alliance that would allow me to inherit his land after his death.
I'm absolutely raging! Having counted on inheriting the rich lands of the north, and the armies stationed there, to defend against the Mori hoard, now I'm left with massive ronin armies on one flank, and Mori sending in wave after wave of attacks on the other.
Should I blame Oda for being a spiteful old git, or should I blame unfair AI cheating for ruining what was shaping up to be a great climax to my campaign?