Last night, playing Takeda on hard, I attacked the Imagawa in Suruga. My ally, Oda, also attacked at the same time and for the first time ever I had a battle with three armies on the field. It was all good fun, we won, but Oda then got to keep the province .

A little while ago, as Oda on hard, I attacked the Shimazu in Higo. My ally Imagawa also attacked, but this time there was no battle (for me at least), and the upshot was I ended up back where I'd come from, the Shimazu army was in its castle, and Imagawa had the province. The same thing then happened the following season in Buzen!

Does the AI always get to keep the goods in these situations, or how does it work?