Yes this is common, it happens in all finite extensive games with perfect knowledge > take someone’s place at a risk board Not the case because Risk has unsha

Yes this is common, it happens in all finite extensive games with perfect knowledge > take someone’s place at a risk board Not the case because Risk has unshared knowledge (the contents of your cards) and taking someone’s place makes it so the game doesn’t have perfect recall. You need shared knowledge and perfect recall, or complete knowledge (in which case recall doesn’t really matter) for a game to have a sub game perfect equilibirium - in simplified terms, for there to be an optimal strategy that applies equally well regardless of the game’s prior events. That might be hard to reason about with Risk, but consider how information “leaks” by when players choose to use their cards or not and when they received the cards. Having a card for a long time but not using it suggests something else than having just received the card, which is why perfect recall is important. For a game to be “stateless” (ie have a one shot sub game perfect equilibrium), when cards were received would also have to not be important, but it is in Risk.